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	$182.26	5.550%	$192.3754	$192.38	$192.40	$192.40
Purchase #2	$141.72	7.174%	$151.887	$151.89	$151.90	$151.90
Purchase #3	$74.91	4.298%	$78.1296	$78.13	$78.15	$78.10
Purchase #4	$72.73	4.304%	$75.8603	$75.86	$75.85	$75.90
Purchase #5	$77.97	9.242%	$85.176	$85.18	$85.20	$85.20
Purchase #6	$29.97	10.359%	$33.0746	$33.07	$33.05	$33.10
Purchase #7	$184.38	12.244%	$206.9555	$206.96	$206.95	$207.00
7 purchase totals =	$763.94		$823.4584	$823.47	$823.50	$823.60