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	$208.56	3.623%	$216.1161	$216.12	$216.10	$216.10
Purchase #2	$191.89	10.596%	$212.2227	$212.22	$212.20	$212.20
Purchase #3	$29.79	10.253%	$32.8444	$32.84	$32.85	$32.80
Purchase #4	$85.94	3.228%	$88.7141	$88.71	$88.70	$88.70
Purchase #5	$126.46	10.385%	$139.5929	$139.59	$139.60	$139.60
Purchase #6	$30.52	5.703%	$32.2606	$32.26	$32.25	$32.30
Purchase #7	$49.71	5.689%	$52.538	$52.54	$52.55	$52.50
7 purchase totals =	$722.87		$774.2888	$774.28	$774.25	$774.20