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	$227.27	11.512%	$253.4333	$253.43	$253.45	$253.40
Purchase #2	$78.87	7.853%	$85.0637	$85.06	$85.05	$85.10
Purchase #3	$141.30	12.136%	$158.4482	$158.45	$158.45	$158.40
Purchase #4	$216.91	3.349%	$224.1743	$224.17	$224.15	$224.20
Purchase #5	$232.66	3.547%	$240.9125	$240.91	$240.90	$240.90
Purchase #6	$67.92	7.724%	$73.1661	$73.17	$73.15	$73.20
Purchase #7	$140.69	10.492%	$155.4512	$155.45	$155.45	$155.50
7 purchase totals =	$1,105.62		$1,190.6493	$1,190.64	$1,190.60	$1,190.70