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	$134.57	8.127%	$145.5065	$145.51	$145.50	$145.50
Purchase #2	$173.75	8.854%	$189.1338	$189.13	$189.15	$189.10
Purchase #3	$101.60	10.774%	$112.5464	$112.55	$112.55	$112.50
Purchase #4	$89.74	12.130%	$100.6255	$100.63	$100.65	$100.60
Purchase #5	$107.76	8.319%	$116.7246	$116.72	$116.70	$116.70
Purchase #6	$194.82	7.554%	$209.5367	$209.54	$209.55	$209.50
Purchase #7	$86.53	7.111%	$92.6831	$92.68	$92.70	$92.70
7 purchase totals =	$888.77		$966.7566	$966.76	$966.80	$966.60