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 $43.80   8.716%   $47.6176   $47.62   $47.60   $47.60  
  Purchase #2 $114.95   3.241%   $118.6755   $118.68   $118.70   $118.70  
  Purchase #3 $54.52   13.698%   $61.9881   $61.99   $62.00   $62.00  
  Purchase #4 $184.77   12.180%   $207.275   $207.28   $207.30   $207.30  
  Purchase #5 $137.46   9.700%   $150.7936   $150.79   $150.80   $150.80  
  Purchase #6 $113.25   10.124%   $124.7154   $124.72   $124.70   $124.70  
  Purchase #7 $45.49   7.344%   $48.8308   $48.83   $48.85   $48.80  
  7 purchase totals = $694.24       $759.8960   $759.91   $759.95   $759.90