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	$40.72	13.754%	$46.3206	$46.32	$46.30	$46.30
Purchase #2	$114.81	11.167%	$127.6308	$127.63	$127.65	$127.60
Purchase #3	$130.99	10.243%	$144.4073	$144.41	$144.40	$144.40
Purchase #4	$191.79	11.150%	$213.1746	$213.17	$213.15	$213.20
Purchase #5	$31.90	4.116%	$33.213	$33.21	$33.20	$33.20
Purchase #6	$39.39	10.762%	$43.6292	$43.63	$43.65	$43.60
Purchase #7	$178.35	6.729%	$190.3512	$190.35	$190.35	$190.40
7 purchase totals =	$727.95		$798.7267	$798.72	$798.70	$798.70