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 $212.26   11.707%   $237.1093   $237.11   $237.10   $237.10  
  Purchase #2 $163.33   12.436%   $183.6417   $183.64   $183.65   $183.60  
  Purchase #3 $85.25   12.189%   $95.6411   $95.64   $95.65   $95.60  
  Purchase #4 $58.75   7.460%   $63.1328   $63.13   $63.15   $63.10  
  Purchase #5 $229.50   7.871%   $247.5639   $247.56   $247.55   $247.60  
  Purchase #6 $109.74   13.249%   $124.2795   $124.28   $124.30   $124.30  
  Purchase #7 $205.42   3.295%   $212.1886   $212.19   $212.20   $212.20  
  7 purchase totals = $1,064.25       $1,163.5569   $1,163.55   $1,163.60   $1,163.50