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	$172.99	9.663%	$189.706	$189.71	$189.70	$189.70
Purchase #2	$104.66	5.535%	$110.4529	$110.45	$110.45	$110.50
Purchase #3	$89.54	13.129%	$101.2957	$101.30	$101.30	$101.30
Purchase #4	$172.76	6.816%	$184.5353	$184.54	$184.55	$184.50
Purchase #5	$116.34	10.483%	$128.5359	$128.54	$128.55	$128.50
Purchase #6	$170.26	13.626%	$193.4596	$193.46	$193.45	$193.50
Purchase #7	$221.51	11.718%	$247.4665	$247.47	$247.45	$247.50
7 purchase totals =	$1,048.06		$1,155.4519	$1,155.47	$1,155.45	$1,155.50