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 $193.77   10.450%   $214.019   $214.02   $214.00   $214.00  
  Purchase #2 $204.27   9.803%   $224.2946   $224.29   $224.30   $224.30  
  Purchase #3 $132.41   13.640%   $150.4707   $150.47   $150.45   $150.50  
  Purchase #4 $187.88   13.224%   $212.7253   $212.73   $212.75   $212.70  
  Purchase #5 $69.86   7.388%   $75.0213   $75.02   $75.00   $75.00  
  Purchase #6 $132.77   4.172%   $138.3092   $138.31   $138.30   $138.30  
  Purchase #7 $40.64   7.456%   $43.6701   $43.67   $43.65   $43.70  
  7 purchase totals = $961.60       $1,058.5102   $1,058.51   $1,058.45   $1,058.50