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 $47.36   4.392%   $49.4401   $49.44   $49.45   $49.40  
  Purchase #2 $145.48   12.387%   $163.5006   $163.50   $163.50   $163.50  
  Purchase #3 $171.55   10.682%   $189.875   $189.88   $189.90   $189.90  
  Purchase #4 $67.58   9.113%   $73.7386   $73.74   $73.75   $73.70  
  Purchase #5 $228.79   12.143%   $256.572   $256.57   $256.55   $256.60  
  Purchase #6 $211.55   6.341%   $224.9644   $224.96   $224.95   $225.00  
  Purchase #7 $88.52   8.209%   $95.7866   $95.79   $95.80   $95.80  
  7 purchase totals = $960.83       $1,053.8773   $1,053.88   $1,053.90   $1,053.90