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	$150.73	5.369%	$158.8227	$158.82	$158.80	$158.80
Purchase #2	$33.28	13.653%	$37.8237	$37.82	$37.80	$37.80
Purchase #3	$55.68	11.138%	$61.8816	$61.88	$61.90	$61.90
Purchase #4	$147.32	4.828%	$154.4326	$154.43	$154.45	$154.40
Purchase #5	$203.94	3.491%	$211.0595	$211.06	$211.05	$211.10
Purchase #6	$189.34	3.154%	$195.3118	$195.31	$195.30	$195.30
Purchase #7	$130.72	13.667%	$148.5855	$148.59	$148.60	$148.60
7 purchase totals =	$911.01		$967.9174	$967.91	$967.90	$967.90