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	$53.54	10.742%	$59.2913	$59.29	$59.30	$59.30
Purchase #2	$12.27	3.809%	$12.7374	$12.74	$12.75	$12.70
Purchase #3	$93.76	7.454%	$100.7489	$100.75	$100.75	$100.70
Purchase #4	$147.45	13.414%	$167.2289	$167.23	$167.25	$167.20
Purchase #5	$195.26	11.159%	$217.0491	$217.05	$217.05	$217.00
Purchase #6	$9.77	11.158%	$10.8601	$10.86	$10.85	$10.90
Purchase #7	$230.71	3.301%	$238.3257	$238.33	$238.35	$238.30
7 purchase totals =	$742.76		$806.2414	$806.25	$806.30	$806.10