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	$209.76	13.761%	$238.6251	$238.63	$238.65	$238.60
Purchase #2	$175.73	13.707%	$199.8173	$199.82	$199.80	$199.80
Purchase #3	$88.89	3.704%	$92.1825	$92.18	$92.20	$92.20
Purchase #4	$247.54	4.203%	$257.9441	$257.94	$257.95	$257.90
Purchase #5	$108.33	9.300%	$118.4047	$118.40	$118.40	$118.40
Purchase #6	$76.28	3.456%	$78.9162	$78.92	$78.90	$78.90
Purchase #7	$86.68	10.264%	$95.5768	$95.58	$95.60	$95.60
7 purchase totals =	$993.21		$1,081.4667	$1,081.47	$1,081.50	$1,081.40