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	$46.95	5.731%	$49.6407	$49.64	$49.65	$49.60
Purchase #2	$217.41	8.834%	$236.616	$236.62	$236.60	$236.60
Purchase #3	$117.74	11.704%	$131.5203	$131.52	$131.50	$131.50
Purchase #4	$89.48	12.776%	$100.912	$100.91	$100.90	$100.90
Purchase #5	$180.89	10.852%	$200.5202	$200.52	$200.50	$200.50
Purchase #6	$247.49	12.521%	$278.4782	$278.48	$278.50	$278.50
Purchase #7	$134.66	11.588%	$150.2644	$150.26	$150.25	$150.30
7 purchase totals =	$1,034.62		$1,147.9518	$1,147.95	$1,147.90	$1,147.90