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	$56.45	9.413%	$61.7636	$61.76	$61.75	$61.80
Purchase #2	$220.52	6.677%	$235.2441	$235.24	$235.25	$235.20
Purchase #3	$94.32	6.486%	$100.4376	$100.44	$100.45	$100.40
Purchase #4	$81.91	12.466%	$92.1209	$92.12	$92.10	$92.10
Purchase #5	$176.98	8.103%	$191.3207	$191.32	$191.30	$191.30
Purchase #6	$250.42	4.755%	$262.3275	$262.33	$262.35	$262.30
Purchase #7	$32.28	4.252%	$33.6525	$33.65	$33.65	$33.70
7 purchase totals =	$912.88		$976.8669	$976.86	$976.85	$976.80