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 $83.48   11.164%   $92.7997   $92.80   $92.80   $92.80  
  Purchase #2 $194.52   12.566%   $218.9634   $218.96   $218.95   $219.00  
  Purchase #3 $162.26   11.116%   $180.2968   $180.30   $180.30   $180.30  
  Purchase #4 $32.66   11.637%   $36.4606   $36.46   $36.45   $36.50  
  Purchase #5 $167.52   12.228%   $188.0043   $188.00   $188.00   $188.00  
  Purchase #6 $154.65   12.791%   $174.4313   $174.43   $174.45   $174.40  
  Purchase #7 $129.75   9.693%   $142.3267   $142.33   $142.35   $142.30  
  7 purchase totals = $924.84       $1,033.2828   $1,033.28   $1,033.30   $1,033.30