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	$68.27	3.624%	$70.7441	$70.74	$70.75	$70.70
Purchase #2	$20.94	5.713%	$22.1363	$22.14	$22.15	$22.10
Purchase #3	$50.34	13.850%	$57.3121	$57.31	$57.30	$57.30
Purchase #4	$78.71	4.857%	$82.5329	$82.53	$82.55	$82.50
Purchase #5	$104.71	7.194%	$112.2428	$112.24	$112.25	$112.20
Purchase #6	$101.33	5.175%	$106.5738	$106.57	$106.55	$106.60
Purchase #7	$30.87	9.141%	$33.6918	$33.69	$33.70	$33.70
7 purchase totals =	$455.17		$485.2338	$485.22	$485.25	$485.10