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 $91.68   3.664%   $95.0392   $95.04   $95.05   $95.00  
  Purchase #2 $53.64   9.572%   $58.7744   $58.77   $58.75   $58.80  
  Purchase #3 $243.99   3.598%   $252.7688   $252.77   $252.75   $252.80  
  Purchase #4 $188.63   5.550%   $199.099   $199.10   $199.10   $199.10  
  Purchase #5 $43.98   3.529%   $45.5321   $45.53   $45.55   $45.50  
  Purchase #6 $183.50   11.201%   $204.0538   $204.05   $204.05   $204.10  
  Purchase #7 $201.90   5.374%   $212.7501   $212.75   $212.75   $212.80  
  7 purchase totals = $1,007.32       $1,068.0174   $1,068.01   $1,068.00   $1,068.10