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 $87.47   8.272%   $94.7055   $94.71   $94.70   $94.70  
  Purchase #2 $200.72   9.740%   $220.2701   $220.27   $220.25   $220.30  
  Purchase #3 $196.65   9.357%   $215.0505   $215.05   $215.05   $215.10  
  Purchase #4 $189.44   8.676%   $205.8758   $205.88   $205.90   $205.90  
  Purchase #5 $65.84   4.717%   $68.9457   $68.95   $68.95   $68.90  
  Purchase #6 $81.29   7.530%   $87.4111   $87.41   $87.40   $87.40  
  Purchase #7 $150.78   7.376%   $161.9015   $161.90   $161.90   $161.90  
  7 purchase totals = $972.19       $1,054.1602   $1,054.17   $1,054.15   $1,054.20