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	$99.29	9.234%	$108.4584	$108.46	$108.45	$108.50
Purchase #2	$29.51	13.209%	$33.408	$33.41	$33.40	$33.40
Purchase #3	$89.32	10.186%	$98.4181	$98.42	$98.40	$98.40
Purchase #4	$166.94	11.693%	$186.4603	$186.46	$186.45	$186.50
Purchase #5	$19.94	10.702%	$22.074	$22.07	$22.05	$22.10
Purchase #6	$240.59	13.300%	$272.5885	$272.59	$272.60	$272.60
Purchase #7	$136.36	6.560%	$145.3052	$145.31	$145.30	$145.30
7 purchase totals =	$781.95		$866.7125	$866.72	$866.65	$866.80