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	$128.27	8.121%	$138.6868	$138.69	$138.70	$138.70
Purchase #2	$90.39	3.284%	$93.3584	$93.36	$93.35	$93.40
Purchase #3	$53.37	3.374%	$55.1707	$55.17	$55.15	$55.20
Purchase #4	$235.98	8.105%	$255.1062	$255.11	$255.10	$255.10
Purchase #5	$111.89	13.551%	$127.0522	$127.05	$127.05	$127.10
Purchase #6	$150.61	12.385%	$169.263	$169.26	$169.25	$169.30
Purchase #7	$64.89	12.315%	$72.8812	$72.88	$72.90	$72.90
7 purchase totals =	$835.40		$911.5185	$911.52	$911.50	$911.70