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	$204.78	3.192%	$211.3166	$211.32	$211.30	$211.30
Purchase #2	$144.26	3.149%	$148.8027	$148.80	$148.80	$148.80
Purchase #3	$136.60	10.714%	$151.2353	$151.24	$151.25	$151.20
Purchase #4	$48.93	3.645%	$50.7135	$50.71	$50.70	$50.70
Purchase #5	$37.88	6.765%	$40.4426	$40.44	$40.45	$40.40
Purchase #6	$84.39	7.622%	$90.8222	$90.82	$90.80	$90.80
Purchase #7	$50.41	8.794%	$54.8431	$54.84	$54.85	$54.80
7 purchase totals =	$707.25		$748.1760	$748.17	$748.15	$748.00