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	$59.78	13.108%	$67.616	$67.62	$67.60	$67.60
Purchase #2	$88.39	8.544%	$95.942	$95.94	$95.95	$95.90
Purchase #3	$144.46	6.741%	$154.198	$154.20	$154.20	$154.20
Purchase #4	$74.57	13.209%	$84.42	$84.42	$84.40	$84.40
Purchase #5	$101.53	3.826%	$105.4145	$105.41	$105.40	$105.40
Purchase #6	$40.82	11.416%	$45.48	$45.48	$45.50	$45.50
Purchase #7	$146.31	8.852%	$159.2614	$159.26	$159.25	$159.30
7 purchase totals =	$655.86		$712.3319	$712.33	$712.30	$712.30