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 $216.65   5.564%   $228.7044   $228.70   $228.70   $228.70  
  Purchase #2 $191.26   12.824%   $215.7872   $215.79   $215.80   $215.80  
  Purchase #3 $160.36   9.498%   $175.591   $175.59   $175.60   $175.60  
  Purchase #4 $58.63   11.155%   $65.1702   $65.17   $65.15   $65.20  
  Purchase #5 $202.76   11.672%   $226.4261   $226.43   $226.45   $226.40  
  Purchase #6 $180.28   6.391%   $191.8017   $191.80   $191.80   $191.80  
  Purchase #7 $66.62   8.574%   $72.332   $72.33   $72.35   $72.30  
  7 purchase totals = $1,076.56       $1,175.8126   $1,175.81   $1,175.85   $1,175.80