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 $213.35   9.726%   $234.1004   $234.10   $234.10   $234.10  
  Purchase #2 $219.84   6.336%   $233.7691   $233.77   $233.75   $233.80  
  Purchase #3 $80.57   9.632%   $88.3305   $88.33   $88.35   $88.30  
  Purchase #4 $241.47   10.689%   $267.2807   $267.28   $267.30   $267.30  
  Purchase #5 $27.65   5.419%   $29.1484   $29.15   $29.15   $29.10  
  Purchase #6 $162.52   11.513%   $181.2309   $181.23   $181.25   $181.20  
  Purchase #7 $18.46   6.152%   $19.5957   $19.60   $19.60   $19.60  
  7 purchase totals = $963.86       $1,053.4557   $1,053.46   $1,053.50   $1,053.40