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 $68.69   5.670%   $72.5847   $72.58   $72.60   $72.60  
  Purchase #2 $236.77   3.467%   $244.9788   $244.98   $245.00   $245.00  
  Purchase #3 $145.70   6.168%   $154.6868   $154.69   $154.70   $154.70  
  Purchase #4 $166.30   8.323%   $180.1411   $180.14   $180.15   $180.10  
  Purchase #5 $95.43   8.308%   $103.3583   $103.36   $103.35   $103.40  
  Purchase #6 $185.90   13.817%   $211.5858   $211.59   $211.60   $211.60  
  Purchase #7 $74.27   8.591%   $80.6505   $80.65   $80.65   $80.70  
  7 purchase totals = $973.06       $1,047.9860   $1,047.99   $1,048.05   $1,048.10