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 $221.30   5.428%   $233.3122   $233.31   $233.30   $233.30  
  Purchase #2 $63.91   8.144%   $69.1148   $69.11   $69.10   $69.10  
  Purchase #3 $101.56   12.764%   $114.5231   $114.52   $114.50   $114.50  
  Purchase #4 $242.92   12.543%   $273.3895   $273.39   $273.40   $273.40  
  Purchase #5 $49.66   6.422%   $52.8492   $52.85   $52.85   $52.80  
  Purchase #6 $141.57   5.120%   $148.8184   $148.82   $148.80   $148.80  
  Purchase #7 $193.54   4.753%   $202.739   $202.74   $202.75   $202.70  
  7 purchase totals = $1,014.46       $1,094.7462   $1,094.74   $1,094.70   $1,094.60