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 $184.32   5.818%   $195.0437   $195.04   $195.05   $195.00  
  Purchase #2 $128.41   5.851%   $135.9233   $135.92   $135.90   $135.90  
  Purchase #3 $148.52   12.329%   $166.831   $166.83   $166.85   $166.80  
  Purchase #4 $19.94   4.124%   $20.7623   $20.76   $20.75   $20.80  
  Purchase #5 $200.86   9.243%   $219.4255   $219.43   $219.45   $219.40  
  Purchase #6 $183.96   10.817%   $203.859   $203.86   $203.85   $203.90  
  Purchase #7 $117.86   12.699%   $132.827   $132.83   $132.85   $132.80  
  7 purchase totals = $983.87       $1,074.6718   $1,074.67   $1,074.70   $1,074.60