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 $216.80   5.675%   $229.1034   $229.10   $229.10   $229.10  
  Purchase #2 $152.55   9.224%   $166.6212   $166.62   $166.60   $166.60  
  Purchase #3 $12.85   13.461%   $14.5797   $14.58   $14.60   $14.60  
  Purchase #4 $226.42   6.744%   $241.6898   $241.69   $241.70   $241.70  
  Purchase #5 $166.70   5.687%   $176.1802   $176.18   $176.20   $176.20  
  Purchase #6 $103.85   9.107%   $113.3076   $113.31   $113.30   $113.30  
  Purchase #7 $194.29   3.784%   $201.6419   $201.64   $201.65   $201.60  
  7 purchase totals = $1,073.46       $1,143.1238   $1,143.12   $1,143.15   $1,143.10