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	$194.67	12.561%	$219.1225	$219.12	$219.10	$219.10
Purchase #2	$56.92	5.300%	$59.9368	$59.94	$59.95	$59.90
Purchase #3	$175.88	8.366%	$190.5941	$190.59	$190.60	$190.60
Purchase #4	$194.52	5.157%	$204.5514	$204.55	$204.55	$204.60
Purchase #5	$228.83	13.546%	$259.8273	$259.83	$259.85	$259.80
Purchase #6	$247.81	4.166%	$258.1338	$258.13	$258.15	$258.10
Purchase #7	$243.84	13.432%	$276.5926	$276.59	$276.60	$276.60
7 purchase totals =	$1,342.47		$1,468.7585	$1,468.75	$1,468.80	$1,468.70