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	$132.85	10.429%	$146.7049	$146.70	$146.70	$146.70
Purchase #2	$87.78	10.860%	$97.3129	$97.31	$97.30	$97.30
Purchase #3	$191.33	4.628%	$200.1848	$200.18	$200.20	$200.20
Purchase #4	$57.64	12.518%	$64.8554	$64.86	$64.85	$64.90
Purchase #5	$241.46	12.423%	$271.4566	$271.46	$271.45	$271.50
Purchase #6	$105.47	3.251%	$108.8988	$108.90	$108.90	$108.90
Purchase #7	$164.69	12.502%	$185.2795	$185.28	$185.30	$185.30
7 purchase totals =	$981.22		$1,074.6929	$1,074.69	$1,074.70	$1,074.80