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 $146.35   10.380%   $161.5411   $161.54   $161.55   $161.50  
  Purchase #2 $24.91   3.374%   $25.7505   $25.75   $25.75   $25.80  
  Purchase #3 $216.57   10.337%   $238.9568   $238.96   $238.95   $239.00  
  Purchase #4 $86.97   11.122%   $96.6428   $96.64   $96.65   $96.60  
  Purchase #5 $238.85   13.269%   $270.543   $270.54   $270.55   $270.50  
  Purchase #6 $147.93   5.770%   $156.4656   $156.47   $156.45   $156.50  
  Purchase #7 $202.70   10.114%   $223.2011   $223.20   $223.20   $223.20  
  7 purchase totals = $1,064.28       $1,173.1009   $1,173.10   $1,173.10   $1,173.10