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	$10.47	11.339%	$11.6572	$11.66	$11.65	$11.70
Purchase #2	$78.53	3.420%	$81.2157	$81.22	$81.20	$81.20
Purchase #3	$154.76	13.667%	$175.911	$175.91	$175.90	$175.90
Purchase #4	$35.81	12.768%	$40.3822	$40.38	$40.40	$40.40
Purchase #5	$184.38	3.281%	$190.4295	$190.43	$190.45	$190.40
Purchase #6	$27.59	6.156%	$29.2884	$29.29	$29.30	$29.30
Purchase #7	$247.73	7.821%	$267.105	$267.11	$267.10	$267.10
7 purchase totals =	$739.27		$795.9890	$796.00	$796.00	$796.00