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 $180.51   7.784%   $194.5609   $194.56   $194.55   $194.60  
  Purchase #2 $108.26   9.308%   $118.3368   $118.34   $118.35   $118.30  
  Purchase #3 $56.71   6.863%   $60.602   $60.60   $60.60   $60.60  
  Purchase #4 $72.98   10.748%   $80.8239   $80.82   $80.80   $80.80  
  Purchase #5 $100.46   5.113%   $105.5965   $105.60   $105.60   $105.60  
  Purchase #6 $216.56   6.241%   $230.0755   $230.08   $230.10   $230.10  
  Purchase #7 $217.96   11.293%   $242.5742   $242.57   $242.55   $242.60  
  7 purchase totals = $953.44       $1,032.5698   $1,032.57   $1,032.55   $1,032.60