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 $211.51   5.508%   $223.16   $223.16   $223.15   $223.20  
  Purchase #2 $124.35   11.243%   $138.3307   $138.33   $138.35   $138.30  
  Purchase #3 $165.69   5.838%   $175.363   $175.36   $175.35   $175.40  
  Purchase #4 $75.93   11.730%   $84.8366   $84.84   $84.85   $84.80  
  Purchase #5 $156.91   10.453%   $173.3118   $173.31   $173.30   $173.30  
  Purchase #6 $49.73   7.845%   $53.6313   $53.63   $53.65   $53.60  
  Purchase #7 $209.89   4.371%   $219.0643   $219.06   $219.05   $219.10  
  7 purchase totals = $994.01       $1,067.6977   $1,067.69   $1,067.70   $1,067.70