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	$196.31	12.427%	$220.7054	$220.71	$220.70	$220.70
Purchase #2	$31.49	10.702%	$34.8601	$34.86	$34.85	$34.90
Purchase #3	$107.42	3.814%	$111.517	$111.52	$111.50	$111.50
Purchase #4	$41.60	12.648%	$46.8616	$46.86	$46.85	$46.90
Purchase #5	$99.25	7.278%	$106.4734	$106.47	$106.45	$106.50
Purchase #6	$191.84	10.700%	$212.3669	$212.37	$212.35	$212.40
Purchase #7	$164.95	8.327%	$178.6854	$178.69	$178.70	$178.70
7 purchase totals =	$832.86		$911.4698	$911.48	$911.40	$911.60