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	$107.41	3.240%	$110.8901	$110.89	$110.90	$110.90
Purchase #2	$52.58	5.126%	$55.2753	$55.28	$55.30	$55.30
Purchase #3	$57.35	4.374%	$59.8585	$59.86	$59.85	$59.90
Purchase #4	$114.45	11.601%	$127.7273	$127.73	$127.75	$127.70
Purchase #5	$213.69	4.712%	$223.7591	$223.76	$223.75	$223.80
Purchase #6	$143.52	3.451%	$148.4729	$148.47	$148.45	$148.50
Purchase #7	$113.57	3.760%	$117.8402	$117.84	$117.85	$117.80
7 purchase totals =	$802.57		$843.8234	$843.83	$843.85	$843.90