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	$133.71	13.447%	$151.69	$151.69	$151.70	$151.70
Purchase #2	$14.99	10.225%	$16.5227	$16.52	$16.50	$16.50
Purchase #3	$218.73	10.540%	$241.7841	$241.78	$241.80	$241.80
Purchase #4	$197.33	12.642%	$222.2765	$222.28	$222.30	$222.30
Purchase #5	$185.65	3.678%	$192.4782	$192.48	$192.50	$192.50
Purchase #6	$238.76	10.736%	$264.3933	$264.39	$264.40	$264.40
Purchase #7	$170.98	11.411%	$190.4905	$190.49	$190.50	$190.50
7 purchase totals =	$1,160.15		$1,279.6353	$1,279.63	$1,279.70	$1,279.70