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 $44.65   4.333%   $46.5847   $46.58   $46.60   $46.60  
  Purchase #2 $183.51   3.513%   $189.9567   $189.96   $189.95   $190.00  
  Purchase #3 $138.87   12.569%   $156.3246   $156.32   $156.30   $156.30  
  Purchase #4 $165.49   4.200%   $172.4406   $172.44   $172.45   $172.40  
  Purchase #5 $160.94   12.864%   $181.6433   $181.64   $181.65   $181.60  
  Purchase #6 $93.55   9.365%   $102.311   $102.31   $102.30   $102.30  
  Purchase #7 $87.64   12.293%   $98.4136   $98.41   $98.40   $98.40  
  7 purchase totals = $874.65       $947.6745   $947.66   $947.65   $947.60