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 $205.89   8.621%   $223.6398   $223.64   $223.65   $223.60  
  Purchase #2 $87.44   11.662%   $97.6373   $97.64   $97.65   $97.60  
  Purchase #3 $231.73   9.233%   $253.1256   $253.13   $253.15   $253.10  
  Purchase #4 $210.64   9.225%   $230.0715   $230.07   $230.05   $230.10  
  Purchase #5 $145.46   13.870%   $165.6353   $165.64   $165.65   $165.60  
  Purchase #6 $193.65   9.389%   $211.8318   $211.83   $211.85   $211.80  
  Purchase #7 $191.58   4.805%   $200.7854   $200.79   $200.80   $200.80  
  7 purchase totals = $1,266.39       $1,382.7267   $1,382.74   $1,382.80   $1,382.60