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 $10.75   4.745%   $11.2601   $11.26   $11.25   $11.30  
  Purchase #2 $64.29   6.160%   $68.2503   $68.25   $68.25   $68.30  
  Purchase #3 $66.52   4.270%   $69.3604   $69.36   $69.35   $69.40  
  Purchase #4 $200.78   12.412%   $225.7008   $225.70   $225.70   $225.70  
  Purchase #5 $238.60   8.474%   $258.819   $258.82   $258.80   $258.80  
  Purchase #6 $173.68   12.766%   $195.852   $195.85   $195.85   $195.90  
  Purchase #7 $174.36   4.451%   $182.1208   $182.12   $182.10   $182.10  
  7 purchase totals = $928.98       $1,011.3634   $1,011.36   $1,011.30   $1,011.50