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 $204.87   7.164%   $219.5469   $219.55   $219.55   $219.50  
  Purchase #2 $197.32   8.593%   $214.2757   $214.28   $214.30   $214.30  
  Purchase #3 $74.88   5.749%   $79.1849   $79.18   $79.20   $79.20  
  Purchase #4 $210.74   4.481%   $220.1833   $220.18   $220.20   $220.20  
  Purchase #5 $23.92   5.541%   $25.2454   $25.25   $25.25   $25.20  
  Purchase #6 $85.89   9.796%   $94.3038   $94.30   $94.30   $94.30  
  Purchase #7 $188.55   6.804%   $201.3789   $201.38   $201.40   $201.40  
  7 purchase totals = $986.17       $1,054.1189   $1,054.12   $1,054.20   $1,054.10