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 $184.84   6.287%   $196.4609   $196.46   $196.45   $196.50  
  Purchase #2 $60.72   4.309%   $63.3364   $63.34   $63.35   $63.30  
  Purchase #3 $160.73   12.630%   $181.0302   $181.03   $181.05   $181.00  
  Purchase #4 $44.82   9.379%   $49.0237   $49.02   $49.00   $49.00  
  Purchase #5 $157.26   13.421%   $178.3659   $178.37   $178.35   $178.40  
  Purchase #6 $176.56   4.398%   $184.3251   $184.33   $184.35   $184.30  
  Purchase #7 $148.62   13.735%   $169.033   $169.03   $169.05   $169.00  
  7 purchase totals = $933.55       $1,021.5752   $1,021.58   $1,021.60   $1,021.50