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	$127.77	9.317%	$139.6743	$139.67	$139.65	$139.70
Purchase #2	$204.57	10.245%	$225.5282	$225.53	$225.55	$225.50
Purchase #3	$38.73	13.414%	$43.9252	$43.93	$43.95	$43.90
Purchase #4	$12.70	6.127%	$13.4781	$13.48	$13.50	$13.50
Purchase #5	$178.82	5.198%	$188.1151	$188.12	$188.10	$188.10
Purchase #6	$70.61	11.419%	$78.673	$78.67	$78.65	$78.70
Purchase #7	$217.38	12.594%	$244.7568	$244.76	$244.75	$244.80
7 purchase totals =	$850.58		$934.1507	$934.16	$934.15	$934.20