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	$90.39	7.159%	$96.861	$96.86	$96.85	$96.90
Purchase #2	$229.39	3.177%	$236.6777	$236.68	$236.70	$236.70
Purchase #3	$55.41	10.518%	$61.238	$61.24	$61.25	$61.20
Purchase #4	$99.72	4.399%	$104.1067	$104.11	$104.10	$104.10
Purchase #5	$130.60	8.228%	$141.3458	$141.35	$141.35	$141.30
Purchase #6	$236.37	13.178%	$267.5188	$267.52	$267.50	$267.50
Purchase #7	$143.29	13.571%	$162.7359	$162.74	$162.75	$162.70
7 purchase totals =	$985.17		$1,070.4839	$1,070.50	$1,070.50	$1,070.40