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 $246.95   8.102%   $266.9579   $266.96   $266.95   $267.00  
  Purchase #2 $195.30   7.313%   $209.5823   $209.58   $209.60   $209.60  
  Purchase #3 $88.61   3.360%   $91.5873   $91.59   $91.60   $91.60  
  Purchase #4 $149.96   10.579%   $165.8243   $165.82   $165.80   $165.80  
  Purchase #5 $109.56   3.754%   $113.6729   $113.67   $113.65   $113.70  
  Purchase #6 $191.69   5.376%   $201.9953   $202.00   $202.00   $202.00  
  Purchase #7 $91.64   8.120%   $99.0812   $99.08   $99.10   $99.10  
  7 purchase totals = $1,073.71       $1,148.7012   $1,148.70   $1,148.70   $1,148.80