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	$55.49	11.328%	$61.7759	$61.78	$61.80	$61.80
Purchase #2	$97.31	12.138%	$109.1215	$109.12	$109.10	$109.10
Purchase #3	$75.47	10.420%	$83.334	$83.33	$83.35	$83.30
Purchase #4	$43.78	3.103%	$45.1385	$45.14	$45.15	$45.10
Purchase #5	$49.65	13.787%	$56.4952	$56.50	$56.50	$56.50
Purchase #6	$131.60	13.379%	$149.2068	$149.21	$149.20	$149.20
Purchase #7	$210.87	9.694%	$231.3117	$231.31	$231.30	$231.30
7 purchase totals =	$664.17		$736.3836	$736.39	$736.40	$736.30