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 $226.47   6.834%   $241.947   $241.95   $241.95   $241.90  
  Purchase #2 $95.39   4.446%   $99.631   $99.63   $99.65   $99.60  
  Purchase #3 $202.46   12.823%   $228.4214   $228.42   $228.40   $228.40  
  Purchase #4 $207.50   4.496%   $216.8292   $216.83   $216.85   $216.80  
  Purchase #5 $142.27   3.392%   $147.0958   $147.10   $147.10   $147.10  
  Purchase #6 $191.33   8.459%   $207.5146   $207.51   $207.50   $207.50  
  Purchase #7 $5.63   7.831%   $6.0709   $6.07   $6.05   $6.10  
  7 purchase totals = $1,071.05       $1,147.5099   $1,147.51   $1,147.50   $1,147.40