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	$73.99	4.155%	$77.0643	$77.06	$77.05	$77.10
Purchase #2	$6.73	13.510%	$7.6392	$7.64	$7.65	$7.60
Purchase #3	$52.60	7.113%	$56.3414	$56.34	$56.35	$56.30
Purchase #4	$30.50	7.196%	$32.6948	$32.69	$32.70	$32.70
Purchase #5	$178.31	10.406%	$196.8649	$196.86	$196.85	$196.90
Purchase #6	$177.48	12.177%	$199.0917	$199.09	$199.10	$199.10
Purchase #7	$73.87	10.825%	$81.8664	$81.87	$81.85	$81.90
7 purchase totals =	$593.48		$651.5627	$651.55	$651.55	$651.60