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 $204.41   7.236%   $219.2011   $219.20   $219.20   $219.20  
  Purchase #2 $186.64   10.770%   $206.7411   $206.74   $206.75   $206.70  
  Purchase #3 $156.68   8.492%   $169.9853   $169.99   $170.00   $170.00  
  Purchase #4 $136.54   6.368%   $145.2349   $145.23   $145.25   $145.20  
  Purchase #5 $181.48   13.281%   $205.5824   $205.58   $205.60   $205.60  
  Purchase #6 $160.83   3.613%   $166.6408   $166.64   $166.65   $166.60  
  Purchase #7 $57.25   6.177%   $60.7863   $60.79   $60.80   $60.80  
  7 purchase totals = $1,083.83       $1,174.1719   $1,174.17   $1,174.25   $1,174.10