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	$52.62	9.144%	$57.4316	$57.43	$57.45	$57.40
Purchase #2	$179.46	11.428%	$199.9687	$199.97	$199.95	$200.00
Purchase #3	$104.64	6.506%	$111.4479	$111.45	$111.45	$111.40
Purchase #4	$146.75	5.159%	$154.3208	$154.32	$154.30	$154.30
Purchase #5	$113.40	9.268%	$123.9099	$123.91	$123.90	$123.90
Purchase #6	$102.71	11.443%	$114.4631	$114.46	$114.45	$114.50
Purchase #7	$160.43	13.370%	$181.8795	$181.88	$181.90	$181.90
7 purchase totals =	$860.01		$943.4215	$943.42	$943.40	$943.40