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 $183.94   7.256%   $197.2867   $197.29   $197.30   $197.30  
  Purchase #2 $229.96   12.613%   $258.9649   $258.96   $258.95   $259.00  
  Purchase #3 $160.97   9.716%   $176.6098   $176.61   $176.60   $176.60  
  Purchase #4 $243.83   4.189%   $254.044   $254.04   $254.05   $254.00  
  Purchase #5 $171.88   9.129%   $187.5709   $187.57   $187.55   $187.60  
  Purchase #6 $225.66   3.251%   $232.9962   $233.00   $233.00   $233.00  
  Purchase #7 $152.29   9.831%   $167.2616   $167.26   $167.25   $167.30  
  7 purchase totals = $1,368.53       $1,474.7341   $1,474.73   $1,474.70   $1,474.80