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 $188.95   7.407%   $202.9455   $202.95   $202.95   $202.90  
  Purchase #2 $184.63   13.824%   $210.1533   $210.15   $210.15   $210.20  
  Purchase #3 $43.48   3.393%   $44.9553   $44.96   $44.95   $45.00  
  Purchase #4 $160.73   5.638%   $169.792   $169.79   $169.80   $169.80  
  Purchase #5 $189.37   12.332%   $212.7231   $212.72   $212.70   $212.70  
  Purchase #6 $150.96   10.102%   $166.21   $166.21   $166.20   $166.20  
  Purchase #7 $154.85   12.648%   $174.4354   $174.44   $174.45   $174.40  
  7 purchase totals = $1,072.97       $1,181.2146   $1,181.22   $1,181.20   $1,181.20