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	$227.83	7.643%	$245.243	$245.24	$245.25	$245.20
Purchase #2	$131.72	12.671%	$148.4102	$148.41	$148.40	$148.40
Purchase #3	$184.75	4.680%	$193.3963	$193.40	$193.40	$193.40
Purchase #4	$98.94	13.734%	$112.5284	$112.53	$112.55	$112.50
Purchase #5	$170.74	7.847%	$184.138	$184.14	$184.15	$184.10
Purchase #6	$90.92	10.427%	$100.4002	$100.40	$100.40	$100.40
Purchase #7	$95.64	7.702%	$103.0062	$103.01	$103.00	$103.00
7 purchase totals =	$1,000.54		$1,087.1223	$1,087.13	$1,087.15	$1,087.00