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 $53.50   12.834%   $60.3662   $60.37   $60.35   $60.40  
  Purchase #2 $186.91   7.290%   $200.5357   $200.54   $200.55   $200.50  
  Purchase #3 $211.31   8.869%   $230.0511   $230.05   $230.05   $230.10  
  Purchase #4 $127.40   8.343%   $138.029   $138.03   $138.05   $138.00  
  Purchase #5 $199.75   9.782%   $219.2895   $219.29   $219.30   $219.30  
  Purchase #6 $56.67   6.762%   $60.502   $60.50   $60.50   $60.50  
  Purchase #7 $182.83   12.530%   $205.7386   $205.74   $205.75   $205.70  
  7 purchase totals = $1,018.37       $1,114.5121   $1,114.52   $1,114.55   $1,114.50