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 $87.26   10.858%   $96.7347   $96.73   $96.75   $96.70  
  Purchase #2 $169.30   8.684%   $184.002   $184.00   $184.00   $184.00  
  Purchase #3 $86.62   4.596%   $90.6011   $90.60   $90.60   $90.60  
  Purchase #4 $210.90   11.353%   $234.8435   $234.84   $234.85   $234.80  
  Purchase #5 $209.65   7.449%   $225.2668   $225.27   $225.25   $225.30  
  Purchase #6 $191.50   11.796%   $214.0893   $214.09   $214.10   $214.10  
  Purchase #7 $166.57   8.444%   $180.6352   $180.64   $180.65   $180.60  
  7 purchase totals = $1,121.80       $1,226.1726   $1,226.17   $1,226.20   $1,226.10