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 $108.75   9.381%   $118.9518   $118.95   $118.95   $119.00  
  Purchase #2 $241.83   11.260%   $269.0601   $269.06   $269.05   $269.10  
  Purchase #3 $21.40   4.248%   $22.3091   $22.31   $22.30   $22.30  
  Purchase #4 $148.99   13.791%   $169.5372   $169.54   $169.55   $169.50  
  Purchase #5 $110.52   13.644%   $125.5993   $125.60   $125.60   $125.60  
  Purchase #6 $60.30   9.179%   $65.8349   $65.83   $65.85   $65.80  
  Purchase #7 $246.47   9.410%   $269.6628   $269.66   $269.65   $269.70  
  7 purchase totals = $938.26       $1,040.9552   $1,040.95   $1,040.95   $1,041.00