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	$92.29	4.754%	$96.6775	$96.68	$96.70	$96.70
Purchase #2	$148.61	5.583%	$156.9069	$156.91	$156.90	$156.90
Purchase #3	$67.70	5.788%	$71.6185	$71.62	$71.60	$71.60
Purchase #4	$231.82	12.313%	$260.364	$260.36	$260.35	$260.40
Purchase #5	$84.61	9.111%	$92.3188	$92.32	$92.30	$92.30
Purchase #6	$93.89	6.276%	$99.7825	$99.78	$99.80	$99.80
Purchase #7	$146.39	3.554%	$151.5927	$151.59	$151.60	$151.60
7 purchase totals =	$865.31		$929.2609	$929.26	$929.25	$929.30