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 $190.27   5.771%   $201.2505   $201.25   $201.25   $201.30  
  Purchase #2 $163.31   4.445%   $170.5691   $170.57   $170.55   $170.60  
  Purchase #3 $26.59   12.462%   $29.9036   $29.90   $29.90   $29.90  
  Purchase #4 $169.88   4.401%   $177.3564   $177.36   $177.35   $177.40  
  Purchase #5 $110.92   3.245%   $114.5194   $114.52   $114.50   $114.50  
  Purchase #6 $115.68   11.521%   $129.0075   $129.01   $129.00   $129.00  
  Purchase #7 $163.96   5.401%   $172.8155   $172.82   $172.80   $172.80  
  7 purchase totals = $940.61       $995.4220   $995.43   $995.35   $995.50