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	$101.50	6.434%	$108.0305	$108.03	$108.05	$108.00
Purchase #2	$224.84	11.376%	$250.4178	$250.42	$250.40	$250.40
Purchase #3	$95.95	13.372%	$108.7804	$108.78	$108.80	$108.80
Purchase #4	$115.79	13.537%	$131.4645	$131.46	$131.45	$131.50
Purchase #5	$147.54	4.186%	$153.716	$153.72	$153.70	$153.70
Purchase #6	$229.80	5.833%	$243.2042	$243.20	$243.20	$243.20
Purchase #7	$145.98	7.264%	$156.584	$156.58	$156.60	$156.60
7 purchase totals =	$1,061.40		$1,152.1974	$1,152.19	$1,152.20	$1,152.20