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	$53.53	13.465%	$60.7378	$60.74	$60.75	$60.70
Purchase #2	$21.52	3.114%	$22.1901	$22.19	$22.20	$22.20
Purchase #3	$155.73	7.766%	$167.824	$167.82	$167.80	$167.80
Purchase #4	$53.73	13.367%	$60.9121	$60.91	$60.90	$60.90
Purchase #5	$76.37	11.842%	$85.4137	$85.41	$85.40	$85.40
Purchase #6	$94.29	5.463%	$99.4411	$99.44	$99.45	$99.40
Purchase #7	$112.31	10.483%	$124.0835	$124.08	$124.10	$124.10
7 purchase totals =	$567.48		$620.6023	$620.59	$620.60	$620.50