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	$170.47	11.500%	$190.0741	$190.07	$190.05	$190.10
Purchase #2	$196.46	9.351%	$214.831	$214.83	$214.85	$214.80
Purchase #3	$12.95	6.768%	$13.8265	$13.83	$13.85	$13.80
Purchase #4	$72.89	3.497%	$75.439	$75.44	$75.45	$75.40
Purchase #5	$88.41	4.394%	$92.2947	$92.29	$92.30	$92.30
Purchase #6	$97.88	13.764%	$111.3522	$111.35	$111.35	$111.40
Purchase #7	$233.47	11.289%	$259.8264	$259.83	$259.85	$259.80
7 purchase totals =	$872.53		$957.6439	$957.64	$957.70	$957.60