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	$47.51	12.404%	$53.4031	$53.40	$53.40	$53.40
Purchase #2	$88.99	7.426%	$95.5984	$95.60	$95.60	$95.60
Purchase #3	$245.85	3.442%	$254.3122	$254.31	$254.30	$254.30
Purchase #4	$190.32	7.698%	$204.9708	$204.97	$204.95	$205.00
Purchase #5	$166.44	12.761%	$187.6794	$187.68	$187.70	$187.70
Purchase #6	$225.48	4.141%	$234.8171	$234.82	$234.80	$234.80
Purchase #7	$48.78	11.711%	$54.4926	$54.49	$54.50	$54.50
7 purchase totals =	$1,013.37		$1,085.2736	$1,085.27	$1,085.25	$1,085.30