Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $196.59   8.612%   $213.5203   $213.52   $213.50   $213.50  
  Purchase #2 $200.98   4.295%   $209.6121   $209.61   $209.60   $209.60  
  Purchase #3 $177.93   13.405%   $201.7815   $201.78   $201.80   $201.80  
  Purchase #4 $212.99   9.528%   $233.2837   $233.28   $233.30   $233.30  
  Purchase #5 $152.76   8.313%   $165.4589   $165.46   $165.45   $165.50  
  Purchase #6 $243.56   5.418%   $256.7561   $256.76   $256.75   $256.80  
  Purchase #7 $141.46   8.355%   $153.279   $153.28   $153.30   $153.30  
  7 purchase totals = $1,326.27       $1,433.6916   $1,433.69   $1,433.70   $1,433.80