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	$115.72	12.734%	$130.4558	$130.46	$130.45	$130.50
Purchase #2	$231.55	10.243%	$255.2677	$255.27	$255.25	$255.30
Purchase #3	$65.69	11.561%	$73.2844	$73.28	$73.30	$73.30
Purchase #4	$171.65	12.791%	$193.6058	$193.61	$193.60	$193.60
Purchase #5	$107.89	7.576%	$116.0637	$116.06	$116.05	$116.10
Purchase #6	$216.35	10.122%	$238.2489	$238.25	$238.25	$238.20
Purchase #7	$172.98	3.797%	$179.5481	$179.55	$179.55	$179.50
7 purchase totals =	$1,081.83		$1,186.4744	$1,186.48	$1,186.45	$1,186.50