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	$103.97	13.544%	$118.0517	$118.05	$118.05	$118.10
Purchase #2	$42.92	6.323%	$45.6338	$45.63	$45.65	$45.60
Purchase #3	$210.41	7.178%	$225.5132	$225.51	$225.50	$225.50
Purchase #4	$222.96	3.106%	$229.8851	$229.89	$229.90	$229.90
Purchase #5	$137.98	5.563%	$145.6558	$145.66	$145.65	$145.70
Purchase #6	$185.29	5.530%	$195.5365	$195.54	$195.55	$195.50
Purchase #7	$136.32	10.599%	$150.7686	$150.77	$150.75	$150.80
7 purchase totals =	$1,039.85		$1,111.0447	$1,111.05	$1,111.05	$1,111.10