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 $214.73   9.363%   $234.8352   $234.84   $234.85   $234.80  
  Purchase #2 $175.95   4.114%   $183.1886   $183.19   $183.20   $183.20  
  Purchase #3 $209.62   4.658%   $219.3841   $219.38   $219.40   $219.40  
  Purchase #4 $12.29   13.323%   $13.9274   $13.93   $13.95   $13.90  
  Purchase #5 $166.95   9.836%   $183.3712   $183.37   $183.35   $183.40  
  Purchase #6 $27.75   6.342%   $29.5099   $29.51   $29.50   $29.50  
  Purchase #7 $188.89   12.428%   $212.3652   $212.37   $212.35   $212.40  
  7 purchase totals = $996.18       $1,076.5816   $1,076.59   $1,076.60   $1,076.60