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	$186.82	4.804%	$195.7948	$195.79	$195.80	$195.80
Purchase #2	$189.63	7.589%	$204.021	$204.02	$204.00	$204.00
Purchase #3	$67.82	6.553%	$72.2642	$72.26	$72.25	$72.30
Purchase #4	$243.40	13.339%	$275.8671	$275.87	$275.85	$275.90
Purchase #5	$90.32	10.613%	$99.9057	$99.91	$99.90	$99.90
Purchase #6	$173.77	8.658%	$188.815	$188.82	$188.80	$188.80
Purchase #7	$126.43	4.629%	$132.2824	$132.28	$132.30	$132.30
7 purchase totals =	$1,078.19		$1,168.9502	$1,168.95	$1,168.90	$1,169.00