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	$184.71	5.771%	$195.3696	$195.37	$195.35	$195.40
Purchase #2	$27.72	6.106%	$29.4126	$29.41	$29.40	$29.40
Purchase #3	$59.40	10.736%	$65.7772	$65.78	$65.80	$65.80
Purchase #4	$66.65	10.785%	$73.8382	$73.84	$73.85	$73.80
Purchase #5	$75.25	4.747%	$78.8221	$78.82	$78.80	$78.80
Purchase #6	$89.35	11.559%	$99.678	$99.68	$99.70	$99.70
Purchase #7	$25.73	4.738%	$26.9491	$26.95	$26.95	$26.90
7 purchase totals =	$528.81		$569.8468	$569.85	$569.85	$569.80