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 $44.89   4.837%   $47.0613   $47.06   $47.05   $47.10  
  Purchase #2 $149.96   6.350%   $159.4825   $159.48   $159.50   $159.50  
  Purchase #3 $248.31   6.697%   $264.9393   $264.94   $264.95   $264.90  
  Purchase #4 $237.80   6.395%   $253.0073   $253.01   $253.00   $253.00  
  Purchase #5 $70.90   3.538%   $73.4084   $73.41   $73.40   $73.40  
  Purchase #6 $116.57   8.814%   $126.8445   $126.84   $126.85   $126.80  
  Purchase #7 $165.82   11.313%   $184.5792   $184.58   $184.60   $184.60  
  7 purchase totals = $1,034.25       $1,109.3225   $1,109.32   $1,109.35   $1,109.30