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 $184.53   9.243%   $201.5861   $201.59   $201.60   $201.60  
  Purchase #2 $151.86   10.526%   $167.8448   $167.84   $167.85   $167.80  
  Purchase #3 $60.70   12.810%   $68.4757   $68.48   $68.50   $68.50  
  Purchase #4 $184.33   12.150%   $206.7261   $206.73   $206.75   $206.70  
  Purchase #5 $213.87   8.476%   $231.9976   $232.00   $232.00   $232.00  
  Purchase #6 $115.35   8.675%   $125.3566   $125.36   $125.35   $125.40  
  Purchase #7 $41.92   3.748%   $43.4912   $43.49   $43.50   $43.50  
  7 purchase totals = $952.56       $1,045.4781   $1,045.49   $1,045.55   $1,045.50