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 $113.88   10.634%   $125.99   $125.99   $126.00   $126.00  
  Purchase #2 $211.64   8.461%   $229.5469   $229.55   $229.55   $229.50  
  Purchase #3 $70.52   4.469%   $73.6715   $73.67   $73.65   $73.70  
  Purchase #4 $38.85   12.232%   $43.6021   $43.60   $43.60   $43.60  
  Purchase #5 $47.49   12.512%   $53.4319   $53.43   $53.45   $53.40  
  Purchase #6 $222.54   10.791%   $246.5543   $246.55   $246.55   $246.60  
  Purchase #7 $170.65   9.756%   $187.2986   $187.30   $187.30   $187.30  
  7 purchase totals = $875.57       $960.0953   $960.09   $960.10   $960.10