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 $70.76   4.819%   $74.1699   $74.17   $74.15   $74.20  
  Purchase #2 $238.68   8.483%   $258.9272   $258.93   $258.95   $258.90  
  Purchase #3 $74.54   6.791%   $79.602   $79.60   $79.60   $79.60  
  Purchase #4 $200.95   9.329%   $219.6966   $219.70   $219.70   $219.70  
  Purchase #5 $88.59   8.679%   $96.2787   $96.28   $96.30   $96.30  
  Purchase #6 $244.95   7.451%   $263.2012   $263.20   $263.20   $263.20  
  Purchase #7 $47.82   11.731%   $53.4298   $53.43   $53.45   $53.40  
  7 purchase totals = $966.29       $1,045.3054   $1,045.31   $1,045.35   $1,045.30