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 $60.33   12.204%   $67.6927   $67.69   $67.70   $67.70  
  Purchase #2 $212.75   10.239%   $234.5335   $234.53   $234.55   $234.50  
  Purchase #3 $189.76   4.633%   $198.5516   $198.55   $198.55   $198.60  
  Purchase #4 $31.72   6.267%   $33.7079   $33.71   $33.70   $33.70  
  Purchase #5 $230.58   5.406%   $243.0452   $243.05   $243.05   $243.00  
  Purchase #6 $161.31   11.564%   $179.9639   $179.96   $179.95   $180.00  
  Purchase #7 $128.29   7.299%   $137.6539   $137.65   $137.65   $137.70  
  7 purchase totals = $1,014.74       $1,095.1487   $1,095.14   $1,095.15   $1,095.20