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	$168.82	9.631%	$185.0791	$185.08	$185.10	$185.10
Purchase #2	$100.31	9.785%	$110.1253	$110.13	$110.15	$110.10
Purchase #3	$176.70	6.398%	$188.0053	$188.01	$188.00	$188.00
Purchase #4	$121.31	9.110%	$132.3613	$132.36	$132.35	$132.40
Purchase #5	$65.96	8.537%	$71.591	$71.59	$71.60	$71.60
Purchase #6	$75.94	12.438%	$85.3854	$85.39	$85.40	$85.40
Purchase #7	$117.50	6.299%	$124.9013	$124.90	$124.90	$124.90
7 purchase totals =	$826.54		$897.4487	$897.46	$897.50	$897.50