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	$80.38	3.707%	$83.3597	$83.36	$83.35	$83.40
Purchase #2	$10.86	11.182%	$12.0744	$12.07	$12.05	$12.10
Purchase #3	$58.52	11.168%	$65.0555	$65.06	$65.05	$65.10
Purchase #4	$74.52	6.734%	$79.5382	$79.54	$79.55	$79.50
Purchase #5	$69.30	6.576%	$73.8572	$73.86	$73.85	$73.90
Purchase #6	$90.39	12.254%	$101.4664	$101.47	$101.45	$101.50
Purchase #7	$47.57	12.615%	$53.571	$53.57	$53.55	$53.60
7 purchase totals =	$431.54		$468.9224	$468.93	$468.85	$469.10