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 $94.95   3.692%   $98.4556   $98.46   $98.45   $98.50  
  Purchase #2 $130.90   3.563%   $135.564   $135.56   $135.55   $135.60  
  Purchase #3 $115.57   7.714%   $124.4851   $124.49   $124.50   $124.50  
  Purchase #4 $120.40   11.569%   $134.3291   $134.33   $134.35   $134.30  
  Purchase #5 $83.84   4.384%   $87.5155   $87.52   $87.50   $87.50  
  Purchase #6 $8.74   12.158%   $9.8026   $9.80   $9.80   $9.80  
  Purchase #7 $106.66   9.552%   $116.8482   $116.85   $116.85   $116.80  
  7 purchase totals = $661.06       $707.0001   $707.01   $707.00   $707.00