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 $60.41   3.179%   $62.3304   $62.33   $62.35   $62.30  
  Purchase #2 $170.58   6.517%   $181.6967   $181.70   $181.70   $181.70  
  Purchase #3 $193.31   5.664%   $204.2591   $204.26   $204.25   $204.30  
  Purchase #4 $144.85   11.133%   $160.9762   $160.98   $161.00   $161.00  
  Purchase #5 $249.94   6.275%   $265.6237   $265.62   $265.60   $265.60  
  Purchase #6 $57.59   6.304%   $61.2205   $61.22   $61.20   $61.20  
  Purchase #7 $210.73   13.530%   $239.2418   $239.24   $239.25   $239.20  
  7 purchase totals = $1,087.41       $1,175.3484   $1,175.35   $1,175.35   $1,175.30