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	$223.47	10.874%	$247.7701	$247.77	$247.75	$247.80
Purchase #2	$73.82	11.483%	$82.2968	$82.30	$82.30	$82.30
Purchase #3	$230.88	5.118%	$242.6964	$242.70	$242.70	$242.70
Purchase #4	$228.37	11.413%	$254.4339	$254.43	$254.45	$254.40
Purchase #5	$124.56	12.288%	$139.8659	$139.87	$139.85	$139.90
Purchase #6	$148.86	7.700%	$160.3222	$160.32	$160.30	$160.30
Purchase #7	$72.43	13.541%	$82.2377	$82.24	$82.25	$82.20
7 purchase totals =	$1,102.39		$1,209.6230	$1,209.63	$1,209.60	$1,209.60