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	$41.31	11.865%	$46.2114	$46.21	$46.20	$46.20
Purchase #2	$109.65	6.195%	$116.4428	$116.44	$116.45	$116.40
Purchase #3	$72.56	13.378%	$82.2671	$82.27	$82.25	$82.30
Purchase #4	$148.54	4.738%	$155.5778	$155.58	$155.60	$155.60
Purchase #5	$70.89	5.235%	$74.6011	$74.60	$74.60	$74.60
Purchase #6	$120.29	4.798%	$126.0615	$126.06	$126.05	$126.10
Purchase #7	$73.60	12.299%	$82.6521	$82.65	$82.65	$82.70
7 purchase totals =	$636.84		$683.8138	$683.81	$683.80	$683.90