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 $43.42   10.459%   $47.9613   $47.96   $47.95   $48.00  
  Purchase #2 $104.86   8.689%   $113.9713   $113.97   $113.95   $114.00  
  Purchase #3 $98.94   9.425%   $108.2651   $108.27   $108.25   $108.30  
  Purchase #4 $198.83   3.651%   $206.0893   $206.09   $206.10   $206.10  
  Purchase #5 $143.82   13.800%   $163.6672   $163.67   $163.65   $163.70  
  Purchase #6 $160.47   13.112%   $181.5108   $181.51   $181.50   $181.50  
  Purchase #7 $110.97   8.657%   $120.5767   $120.58   $120.60   $120.60  
  7 purchase totals = $861.31       $942.0417   $942.05   $942.00   $942.20