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	$176.75	11.294%	$196.7121	$196.71	$196.70	$196.70
Purchase #2	$228.33	5.471%	$240.8219	$240.82	$240.80	$240.80
Purchase #3	$173.93	12.738%	$196.0852	$196.09	$196.10	$196.10
Purchase #4	$105.85	6.602%	$112.8382	$112.84	$112.85	$112.80
Purchase #5	$33.87	3.290%	$34.9843	$34.98	$35.00	$35.00
Purchase #6	$245.44	13.647%	$278.9352	$278.94	$278.95	$278.90
Purchase #7	$19.80	7.466%	$21.2783	$21.28	$21.30	$21.30
7 purchase totals =	$983.97		$1,081.6552	$1,081.66	$1,081.70	$1,081.60