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	$38.91	6.236%	$41.3364	$41.34	$41.35	$41.30
Purchase #2	$100.32	8.257%	$108.6034	$108.60	$108.60	$108.60
Purchase #3	$137.53	6.847%	$146.9467	$146.95	$146.95	$146.90
Purchase #4	$143.96	8.784%	$156.6054	$156.61	$156.60	$156.60
Purchase #5	$248.50	4.422%	$259.4887	$259.49	$259.50	$259.50
Purchase #6	$128.69	9.783%	$141.2797	$141.28	$141.30	$141.30
Purchase #7	$177.64	12.518%	$199.877	$199.88	$199.90	$199.90
7 purchase totals =	$975.55		$1,054.1373	$1,054.15	$1,054.20	$1,054.10