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 $169.28   10.497%   $187.0493   $187.05   $187.05   $187.00  
  Purchase #2 $47.99   13.336%   $54.3899   $54.39   $54.40   $54.40  
  Purchase #3 $215.37   9.534%   $235.9034   $235.90   $235.90   $235.90  
  Purchase #4 $17.96   8.687%   $19.5202   $19.52   $19.50   $19.50  
  Purchase #5 $103.93   10.424%   $114.7637   $114.76   $114.75   $114.80  
  Purchase #6 $170.98   6.221%   $181.6167   $181.62   $181.60   $181.60  
  Purchase #7 $226.98   10.623%   $251.0921   $251.09   $251.10   $251.10  
  7 purchase totals = $952.49       $1,044.3353   $1,044.33   $1,044.30   $1,044.30