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 $86.59   10.227%   $95.4456   $95.45   $95.45   $95.40  
  Purchase #2 $156.65   9.372%   $171.3312   $171.33   $171.35   $171.30  
  Purchase #3 $245.71   11.452%   $273.8487   $273.85   $273.85   $273.80  
  Purchase #4 $227.96   7.251%   $244.4894   $244.49   $244.50   $244.50  
  Purchase #5 $11.89   10.534%   $13.1425   $13.14   $13.15   $13.10  
  Purchase #6 $203.70   10.585%   $225.2616   $225.26   $225.25   $225.30  
  Purchase #7 $220.27   8.180%   $238.2881   $238.29   $238.30   $238.30  
  7 purchase totals = $1,152.77       $1,261.8071   $1,261.81   $1,261.85   $1,261.70