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	$155.50	13.142%	$175.9358	$175.94	$175.95	$175.90
Purchase #2	$147.69	10.194%	$162.7455	$162.75	$162.75	$162.70
Purchase #3	$131.40	8.161%	$142.1236	$142.12	$142.10	$142.10
Purchase #4	$200.54	12.520%	$225.6476	$225.65	$225.65	$225.60
Purchase #5	$47.89	13.342%	$54.2795	$54.28	$54.30	$54.30
Purchase #6	$224.81	13.195%	$254.4737	$254.47	$254.45	$254.50
Purchase #7	$195.29	8.614%	$212.1123	$212.11	$212.10	$212.10
7 purchase totals =	$1,103.12		$1,227.3180	$1,227.32	$1,227.30	$1,227.20