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	$152.43	11.196%	$169.4961	$169.50	$169.50	$169.50
Purchase #2	$67.66	12.579%	$76.171	$76.17	$76.15	$76.20
Purchase #3	$163.59	7.209%	$175.3832	$175.38	$175.40	$175.40
Purchase #4	$65.50	9.647%	$71.8188	$71.82	$71.80	$71.80
Purchase #5	$62.64	4.353%	$65.3667	$65.37	$65.35	$65.40
Purchase #6	$10.27	11.220%	$11.4223	$11.42	$11.40	$11.40
Purchase #7	$160.33	8.225%	$173.5171	$173.52	$173.50	$173.50
7 purchase totals =	$682.42		$743.1752	$743.18	$743.10	$743.20