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	$152.36	3.838%	$158.2076	$158.21	$158.20	$158.20
Purchase #2	$100.39	4.776%	$105.1846	$105.18	$105.20	$105.20
Purchase #3	$91.34	13.320%	$103.5065	$103.51	$103.50	$103.50
Purchase #4	$69.52	4.415%	$72.5893	$72.59	$72.60	$72.60
Purchase #5	$28.64	6.672%	$30.5509	$30.55	$30.55	$30.60
Purchase #6	$158.60	8.200%	$171.6052	$171.61	$171.60	$171.60
Purchase #7	$138.75	10.803%	$153.7392	$153.74	$153.75	$153.70
7 purchase totals =	$739.60		$795.3833	$795.39	$795.40	$795.40