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	$238.60	7.453%	$256.3829	$256.38	$256.40	$256.40
Purchase #2	$89.77	10.364%	$99.0738	$99.07	$99.05	$99.10
Purchase #3	$108.72	7.747%	$117.1425	$117.14	$117.15	$117.10
Purchase #4	$111.30	6.411%	$118.4354	$118.44	$118.45	$118.40
Purchase #5	$102.99	8.472%	$111.7153	$111.72	$111.70	$111.70
Purchase #6	$88.66	4.623%	$92.7588	$92.76	$92.75	$92.80
Purchase #7	$226.25	3.789%	$234.8226	$234.82	$234.80	$234.80
7 purchase totals =	$966.29		$1,030.3313	$1,030.33	$1,030.30	$1,030.30