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	$97.40	6.237%	$103.4748	$103.47	$103.45	$103.50
Purchase #2	$125.43	11.568%	$139.9397	$139.94	$139.95	$139.90
Purchase #3	$141.87	13.222%	$160.6281	$160.63	$160.65	$160.60
Purchase #4	$124.35	10.471%	$137.3707	$137.37	$137.35	$137.40
Purchase #5	$131.52	10.665%	$145.5466	$145.55	$145.55	$145.50
Purchase #6	$155.54	11.136%	$172.8609	$172.86	$172.85	$172.90
Purchase #7	$137.71	10.736%	$152.4945	$152.49	$152.50	$152.50
7 purchase totals =	$913.82		$1,012.3153	$1,012.31	$1,012.30	$1,012.30