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 $232.66   6.572%   $247.9504   $247.95   $247.95   $248.00  
  Purchase #2 $170.66   12.512%   $192.013   $192.01   $192.00   $192.00  
  Purchase #3 $157.93   7.410%   $169.6326   $169.63   $169.65   $169.60  
  Purchase #4 $22.44   10.718%   $24.8451   $24.85   $24.85   $24.80  
  Purchase #5 $118.35   5.364%   $124.6983   $124.70   $124.70   $124.70  
  Purchase #6 $181.58   5.651%   $191.8411   $191.84   $191.85   $191.80  
  Purchase #7 $220.59   10.845%   $244.513   $244.51   $244.50   $244.50  
  7 purchase totals = $1,104.21       $1,195.4935   $1,195.49   $1,195.50   $1,195.40