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	$214.79	4.119%	$223.6372	$223.64	$223.65	$223.60
Purchase #2	$5.41	12.286%	$6.0747	$6.07	$6.05	$6.10
Purchase #3	$173.73	6.683%	$185.3404	$185.34	$185.35	$185.30
Purchase #4	$51.53	4.394%	$53.7942	$53.79	$53.80	$53.80
Purchase #5	$144.70	3.822%	$150.2304	$150.23	$150.25	$150.20
Purchase #6	$52.93	4.779%	$55.4595	$55.46	$55.45	$55.50
Purchase #7	$10.79	13.714%	$12.2697	$12.27	$12.25	$12.30
7 purchase totals =	$653.88		$686.8061	$686.80	$686.80	$686.80