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 $43.34   5.234%   $45.6084   $45.61   $45.60   $45.60  
  Purchase #2 $217.62   7.477%   $233.8914   $233.89   $233.90   $233.90  
  Purchase #3 $73.29   3.291%   $75.702   $75.70   $75.70   $75.70  
  Purchase #4 $200.86   5.805%   $212.5199   $212.52   $212.50   $212.50  
  Purchase #5 $107.51   12.138%   $120.5596   $120.56   $120.55   $120.60  
  Purchase #6 $134.55   11.332%   $149.7972   $149.80   $149.80   $149.80  
  Purchase #7 $191.56   6.190%   $203.4176   $203.42   $203.40   $203.40  
  7 purchase totals = $968.73       $1,041.4961   $1,041.50   $1,041.45   $1,041.50