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	$9.88	8.661%	$10.7357	$10.74	$10.75	$10.70
Purchase #2	$64.61	4.466%	$67.4955	$67.50	$67.50	$67.50
Purchase #3	$100.52	11.180%	$111.7581	$111.76	$111.75	$111.80
Purchase #4	$45.95	4.296%	$47.924	$47.92	$47.90	$47.90
Purchase #5	$249.35	8.684%	$271.0036	$271.00	$271.00	$271.00
Purchase #6	$22.59	5.766%	$23.8925	$23.89	$23.90	$23.90
Purchase #7	$170.36	11.296%	$189.6039	$189.60	$189.60	$189.60
7 purchase totals =	$663.26		$722.4133	$722.41	$722.40	$722.40