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	$235.80	11.789%	$263.5985	$263.60	$263.60	$263.60
Purchase #2	$159.62	3.266%	$164.8332	$164.83	$164.85	$164.80
Purchase #3	$48.74	4.201%	$50.7876	$50.79	$50.80	$50.80
Purchase #4	$78.26	12.635%	$88.1482	$88.15	$88.15	$88.10
Purchase #5	$213.59	4.574%	$223.3596	$223.36	$223.35	$223.40
Purchase #6	$143.87	12.315%	$161.5876	$161.59	$161.60	$161.60
Purchase #7	$163.55	5.228%	$172.1004	$172.10	$172.10	$172.10
7 purchase totals =	$1,043.43		$1,124.4151	$1,124.42	$1,124.45	$1,124.40