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 $174.67   5.714%   $184.6506   $184.65   $184.65   $184.70  
  Purchase #2 $223.29   10.597%   $246.952   $246.95   $246.95   $247.00  
  Purchase #3 $94.44   13.687%   $107.366   $107.37   $107.35   $107.40  
  Purchase #4 $59.55   10.385%   $65.7343   $65.73   $65.75   $65.70  
  Purchase #5 $34.35   5.642%   $36.288   $36.29   $36.30   $36.30  
  Purchase #6 $98.96   9.308%   $108.1712   $108.17   $108.15   $108.20  
  Purchase #7 $127.33   6.806%   $135.9961   $136.00   $136.00   $136.00  
  7 purchase totals = $812.59       $885.1582   $885.16   $885.15   $885.30