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	$11.47	8.445%	$12.4386	$12.44	$12.45	$12.40
Purchase #2	$171.63	11.741%	$191.7811	$191.78	$191.80	$191.80
Purchase #3	$90.85	10.657%	$100.5319	$100.53	$100.55	$100.50
Purchase #4	$166.79	3.778%	$173.0913	$173.09	$173.10	$173.10
Purchase #5	$120.25	7.749%	$129.5682	$129.57	$129.55	$129.60
Purchase #6	$211.28	9.544%	$231.4446	$231.44	$231.45	$231.40
Purchase #7	$195.95	13.415%	$222.2367	$222.24	$222.25	$222.20
7 purchase totals =	$968.22		$1,061.0924	$1,061.09	$1,061.15	$1,061.00