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	$161.74	13.474%	$183.5328	$183.53	$183.55	$183.50
Purchase #2	$38.82	4.370%	$40.5164	$40.52	$40.50	$40.50
Purchase #3	$217.93	12.497%	$245.1647	$245.16	$245.15	$245.20
Purchase #4	$87.35	5.756%	$92.3779	$92.38	$92.40	$92.40
Purchase #5	$184.71	6.103%	$195.9829	$195.98	$196.00	$196.00
Purchase #6	$55.26	5.132%	$58.0959	$58.10	$58.10	$58.10
Purchase #7	$239.51	11.417%	$266.8549	$266.85	$266.85	$266.90
7 purchase totals =	$985.32		$1,082.5255	$1,082.52	$1,082.55	$1,082.60