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	$135.41	12.516%	$152.3579	$152.36	$152.35	$152.40
Purchase #2	$95.72	5.132%	$100.6324	$100.63	$100.65	$100.60
Purchase #3	$107.83	6.201%	$114.5165	$114.52	$114.50	$114.50
Purchase #4	$145.99	5.324%	$153.7625	$153.76	$153.75	$153.80
Purchase #5	$198.62	13.839%	$226.107	$226.11	$226.10	$226.10
Purchase #6	$54.72	12.412%	$61.5118	$61.51	$61.50	$61.50
Purchase #7	$242.25	6.535%	$258.081	$258.08	$258.10	$258.10
7 purchase totals =	$980.54		$1,066.9691	$1,066.97	$1,066.95	$1,067.00