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	$209.79	9.547%	$229.8187	$229.82	$229.80	$229.80
Purchase #2	$230.92	11.192%	$256.7646	$256.76	$256.75	$256.80
Purchase #3	$57.56	5.719%	$60.8519	$60.85	$60.85	$60.90
Purchase #4	$69.95	12.533%	$78.7168	$78.72	$78.70	$78.70
Purchase #5	$127.76	4.150%	$133.062	$133.06	$133.05	$133.10
Purchase #6	$176.63	10.857%	$195.8067	$195.81	$195.80	$195.80
Purchase #7	$88.70	12.543%	$99.8256	$99.83	$99.85	$99.80
7 purchase totals =	$961.31		$1,054.8463	$1,054.85	$1,054.80	$1,054.90