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 $32.35   12.414%   $36.3659   $36.37   $36.35   $36.40  
  Purchase #2 $113.84   10.374%   $125.6498   $125.65   $125.65   $125.60  
  Purchase #3 $166.75   9.102%   $181.9276   $181.93   $181.95   $181.90  
  Purchase #4 $176.85   10.261%   $194.9966   $195.00   $195.00   $195.00  
  Purchase #5 $149.30   7.625%   $160.6841   $160.68   $160.70   $160.70  
  Purchase #6 $231.27   11.696%   $258.3193   $258.32   $258.30   $258.30  
  Purchase #7 $152.60   10.509%   $168.6367   $168.64   $168.65   $168.60  
  7 purchase totals = $1,022.96       $1,126.5800   $1,126.59   $1,126.60   $1,126.50