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	$55.40	10.326%	$61.1206	$61.12	$61.10	$61.10
Purchase #2	$135.78	11.262%	$151.0715	$151.07	$151.05	$151.10
Purchase #3	$222.33	3.714%	$230.5873	$230.59	$230.60	$230.60
Purchase #4	$115.82	7.274%	$124.2447	$124.24	$124.25	$124.20
Purchase #5	$159.90	3.564%	$165.5988	$165.60	$165.60	$165.60
Purchase #6	$46.77	13.370%	$53.0231	$53.02	$53.00	$53.00
Purchase #7	$204.93	10.849%	$227.1629	$227.16	$227.15	$227.20
7 purchase totals =	$940.93		$1,012.8089	$1,012.80	$1,012.75	$1,012.80