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	$134.56	12.836%	$151.8321	$151.83	$151.85	$151.80
Purchase #2	$116.93	11.127%	$129.9408	$129.94	$129.95	$129.90
Purchase #3	$62.93	6.584%	$67.0733	$67.07	$67.05	$67.10
Purchase #4	$236.81	13.764%	$269.4045	$269.40	$269.40	$269.40
Purchase #5	$186.39	11.612%	$208.0336	$208.03	$208.05	$208.00
Purchase #6	$87.66	9.414%	$95.9123	$95.91	$95.90	$95.90
Purchase #7	$148.32	3.435%	$153.4148	$153.41	$153.40	$153.40
7 purchase totals =	$973.60		$1,075.6114	$1,075.59	$1,075.60	$1,075.50