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 $23.82   8.275%   $25.7911   $25.79   $25.80   $25.80  
  Purchase #2 $205.47   6.744%   $219.3269   $219.33   $219.35   $219.30  
  Purchase #3 $52.81   4.112%   $54.9815   $54.98   $55.00   $55.00  
  Purchase #4 $166.59   9.269%   $182.0312   $182.03   $182.05   $182.00  
  Purchase #5 $163.44   9.817%   $179.4849   $179.48   $179.50   $179.50  
  Purchase #6 $221.85   5.805%   $234.7284   $234.73   $234.75   $234.70  
  Purchase #7 $223.96   6.394%   $238.28   $238.28   $238.30   $238.30  
  7 purchase totals = $1,057.94       $1,134.6240   $1,134.62   $1,134.75   $1,134.60