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 $97.64   5.151%   $102.6694   $102.67   $102.65   $102.70  
  Purchase #2 $204.91   13.374%   $232.3147   $232.31   $232.30   $232.30  
  Purchase #3 $180.37   3.263%   $186.2555   $186.26   $186.25   $186.30  
  Purchase #4 $127.61   12.352%   $143.3724   $143.37   $143.35   $143.40  
  Purchase #5 $200.91   5.518%   $211.9962   $212.00   $212.00   $212.00  
  Purchase #6 $180.55   6.188%   $191.7224   $191.72   $191.70   $191.70  
  Purchase #7 $186.93   3.791%   $194.0165   $194.02   $194.00   $194.00  
  7 purchase totals = $1,178.92       $1,262.3471   $1,262.35   $1,262.25   $1,262.40