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	$177.54	4.347%	$185.2577	$185.26	$185.25	$185.30
Purchase #2	$180.72	11.186%	$200.9353	$200.94	$200.95	$200.90
Purchase #3	$48.75	12.594%	$54.8896	$54.89	$54.90	$54.90
Purchase #4	$58.71	5.349%	$61.8504	$61.85	$61.85	$61.90
Purchase #5	$174.86	8.150%	$189.1111	$189.11	$189.10	$189.10
Purchase #6	$139.27	5.586%	$147.0496	$147.05	$147.05	$147.00
Purchase #7	$114.87	4.601%	$120.1552	$120.16	$120.15	$120.20
7 purchase totals =	$894.72		$959.2489	$959.26	$959.25	$959.30