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	$129.44	13.512%	$146.9299	$146.93	$146.95	$146.90
Purchase #2	$73.92	13.521%	$83.9147	$83.91	$83.90	$83.90
Purchase #3	$72.72	13.163%	$82.2921	$82.29	$82.30	$82.30
Purchase #4	$56.55	3.236%	$58.38	$58.38	$58.40	$58.40
Purchase #5	$188.54	6.323%	$200.4614	$200.46	$200.45	$200.50
Purchase #6	$59.35	5.119%	$62.3881	$62.39	$62.40	$62.40
Purchase #7	$146.41	10.423%	$161.6703	$161.67	$161.65	$161.70
7 purchase totals =	$726.93		$796.0365	$796.03	$796.05	$796.10