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	$173.42	12.399%	$194.9223	$194.92	$194.90	$194.90
Purchase #2	$170.89	4.682%	$178.8911	$178.89	$178.90	$178.90
Purchase #3	$15.89	11.708%	$17.7504	$17.75	$17.75	$17.80
Purchase #4	$78.91	4.537%	$82.4901	$82.49	$82.50	$82.50
Purchase #5	$188.64	13.749%	$214.5761	$214.58	$214.60	$214.60
Purchase #6	$72.35	13.117%	$81.8401	$81.84	$81.85	$81.80
Purchase #7	$206.51	10.774%	$228.7594	$228.76	$228.75	$228.80
7 purchase totals =	$906.61		$999.2295	$999.23	$999.25	$999.30