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	$108.84	9.585%	$119.2723	$119.27	$119.25	$119.30
Purchase #2	$11.53	5.415%	$12.1543	$12.15	$12.15	$12.20
Purchase #3	$22.84	11.726%	$25.5182	$25.52	$25.50	$25.50
Purchase #4	$24.73	4.216%	$25.7726	$25.77	$25.75	$25.80
Purchase #5	$109.76	12.536%	$123.5195	$123.52	$123.50	$123.50
Purchase #6	$65.71	10.325%	$72.4946	$72.49	$72.50	$72.50
Purchase #7	$42.89	10.796%	$47.5204	$47.52	$47.50	$47.50
7 purchase totals =	$386.30		$426.2519	$426.24	$426.15	$426.30