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 $237.29   11.204%   $263.876   $263.88   $263.90   $263.90  
  Purchase #2 $119.94   9.787%   $131.6785   $131.68   $131.70   $131.70  
  Purchase #3 $91.62   4.558%   $95.796   $95.80   $95.80   $95.80  
  Purchase #4 $205.31   11.467%   $228.8529   $228.85   $228.85   $228.90  
  Purchase #5 $68.56   3.235%   $70.7779   $70.78   $70.80   $70.80  
  Purchase #6 $215.26   8.637%   $233.852   $233.85   $233.85   $233.90  
  Purchase #7 $120.65   4.455%   $126.025   $126.03   $126.05   $126.00  
  7 purchase totals = $1,058.63       $1,150.8583   $1,150.87   $1,150.95   $1,151.00