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 $61.50   12.126%   $68.9575   $68.96   $68.95   $69.00  
  Purchase #2 $116.81   5.174%   $122.8537   $122.85   $122.85   $122.90  
  Purchase #3 $222.68   4.616%   $232.9589   $232.96   $232.95   $233.00  
  Purchase #4 $214.77   13.540%   $243.8499   $243.85   $243.85   $243.80  
  Purchase #5 $140.43   3.464%   $145.2945   $145.29   $145.30   $145.30  
  Purchase #6 $88.32   9.611%   $96.8084   $96.81   $96.80   $96.80  
  Purchase #7 $182.29   5.487%   $192.2923   $192.29   $192.30   $192.30  
  7 purchase totals = $1,026.80       $1,103.0152   $1,103.01   $1,103.00   $1,103.10