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	$91.31	13.314%	$103.467	$103.47	$103.45	$103.50
Purchase #2	$173.95	5.368%	$183.2876	$183.29	$183.30	$183.30
Purchase #3	$147.86	9.196%	$161.4572	$161.46	$161.45	$161.50
Purchase #4	$79.48	8.117%	$85.9314	$85.93	$85.95	$85.90
Purchase #5	$24.71	3.485%	$25.5711	$25.57	$25.55	$25.60
Purchase #6	$131.67	10.790%	$145.8772	$145.88	$145.90	$145.90
Purchase #7	$55.27	4.781%	$57.9125	$57.91	$57.90	$57.90
7 purchase totals =	$704.25		$763.5040	$763.51	$763.50	$763.60