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 $54.44   7.713%   $58.639   $58.64   $58.65   $58.60  
  Purchase #2 $226.37   9.317%   $247.4609   $247.46   $247.45   $247.50  
  Purchase #3 $32.54   7.450%   $34.9642   $34.96   $34.95   $35.00  
  Purchase #4 $167.48   3.757%   $173.7722   $173.77   $173.75   $173.80  
  Purchase #5 $120.94   4.570%   $126.467   $126.47   $126.45   $126.50  
  Purchase #6 $179.62   7.380%   $192.876   $192.88   $192.90   $192.90  
  Purchase #7 $230.33   10.534%   $254.593   $254.59   $254.60   $254.60  
  7 purchase totals = $1,011.72       $1,088.7723   $1,088.77   $1,088.75   $1,088.90