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 $145.83   4.821%   $152.8605   $152.86   $152.85   $152.90  
  Purchase #2 $62.31   5.283%   $65.6018   $65.60   $65.60   $65.60  
  Purchase #3 $184.89   10.171%   $203.6952   $203.70   $203.70   $203.70  
  Purchase #4 $248.40   6.647%   $264.9111   $264.91   $264.90   $264.90  
  Purchase #5 $207.86   11.595%   $231.9614   $231.96   $231.95   $232.00  
  Purchase #6 $236.69   6.620%   $252.3589   $252.36   $252.35   $252.40  
  Purchase #7 $74.52   9.341%   $81.4809   $81.48   $81.50   $81.50  
  7 purchase totals = $1,160.50       $1,252.8698   $1,252.87   $1,252.85   $1,253.00