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 $203.57   5.295%   $214.349   $214.35   $214.35   $214.30  
  Purchase #2 $197.45   7.351%   $211.9645   $211.96   $211.95   $212.00  
  Purchase #3 $58.54   10.395%   $64.6252   $64.63   $64.65   $64.60  
  Purchase #4 $177.80   7.760%   $191.5973   $191.60   $191.60   $191.60  
  Purchase #5 $146.62   4.357%   $153.0082   $153.01   $153.00   $153.00  
  Purchase #6 $33.39   8.843%   $36.3427   $36.34   $36.35   $36.30  
  Purchase #7 $152.82   8.514%   $165.8311   $165.83   $165.85   $165.80  
  7 purchase totals = $970.19       $1,037.7180   $1,037.72   $1,037.75   $1,037.60