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	$85.52	10.602%	$94.5868	$94.59	$94.60	$94.60
Purchase #2	$78.77	13.174%	$89.1472	$89.15	$89.15	$89.10
Purchase #3	$210.65	11.748%	$235.3972	$235.40	$235.40	$235.40
Purchase #4	$228.62	9.453%	$250.2314	$250.23	$250.25	$250.20
Purchase #5	$195.42	10.789%	$216.5039	$216.50	$216.50	$216.50
Purchase #6	$44.79	4.872%	$46.9722	$46.97	$46.95	$47.00
Purchase #7	$237.50	12.865%	$268.0544	$268.05	$268.05	$268.10
7 purchase totals =	$1,081.27		$1,200.8931	$1,200.89	$1,200.90	$1,200.90