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	$234.80	10.477%	$259.4	$259.40	$259.40	$259.40
Purchase #2	$77.91	9.386%	$85.2226	$85.22	$85.20	$85.20
Purchase #3	$19.50	6.360%	$20.7402	$20.74	$20.75	$20.70
Purchase #4	$78.47	13.266%	$88.8798	$88.88	$88.90	$88.90
Purchase #5	$132.76	7.656%	$142.9241	$142.92	$142.90	$142.90
Purchase #6	$54.39	4.169%	$56.6575	$56.66	$56.65	$56.70
Purchase #7	$232.78	3.748%	$241.5046	$241.50	$241.50	$241.50
7 purchase totals =	$830.61		$895.3288	$895.32	$895.30	$895.30