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	$214.28	4.200%	$223.2798	$223.28	$223.30	$223.30
Purchase #2	$228.32	3.728%	$236.8318	$236.83	$236.85	$236.80
Purchase #3	$57.61	5.413%	$60.7284	$60.73	$60.75	$60.70
Purchase #4	$162.34	7.498%	$174.5123	$174.51	$174.50	$174.50
Purchase #5	$37.67	13.513%	$42.7603	$42.76	$42.75	$42.80
Purchase #6	$29.91	10.320%	$32.9967	$33.00	$33.00	$33.00
Purchase #7	$90.69	9.389%	$99.2049	$99.20	$99.20	$99.20
7 purchase totals =	$820.82		$870.3142	$870.31	$870.35	$870.30