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 $230.98   5.860%   $244.5154   $244.52   $244.50   $244.50  
  Purchase #2 $59.44   4.292%   $61.9912   $61.99   $62.00   $62.00  
  Purchase #3 $130.32   6.207%   $138.409   $138.41   $138.40   $138.40  
  Purchase #4 $181.96   13.328%   $206.2116   $206.21   $206.20   $206.20  
  Purchase #5 $191.99   11.200%   $213.4929   $213.49   $213.50   $213.50  
  Purchase #6 $58.84   13.403%   $66.7263   $66.73   $66.75   $66.70  
  Purchase #7 $149.65   11.313%   $166.5799   $166.58   $166.60   $166.60  
  7 purchase totals = $1,003.18       $1,097.9263   $1,097.93   $1,097.95   $1,097.90