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	$49.32	8.359%	$53.4427	$53.44	$53.45	$53.40
Purchase #2	$62.66	8.250%	$67.8295	$67.83	$67.85	$67.80
Purchase #3	$7.94	6.821%	$8.4816	$8.48	$8.50	$8.50
Purchase #4	$29.57	12.173%	$33.1696	$33.17	$33.15	$33.20
Purchase #5	$83.49	11.120%	$92.7741	$92.77	$92.75	$92.80
Purchase #6	$50.63	9.518%	$55.449	$55.45	$55.45	$55.40
Purchase #7	$226.25	11.106%	$251.3773	$251.38	$251.40	$251.40
7 purchase totals =	$509.86		$562.5238	$562.52	$562.55	$562.50