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	$243.86	8.630%	$264.9051	$264.91	$264.90	$264.90
Purchase #2	$217.69	10.838%	$241.2832	$241.28	$241.30	$241.30
Purchase #3	$19.31	8.169%	$20.8874	$20.89	$20.90	$20.90
Purchase #4	$88.25	5.629%	$93.2176	$93.22	$93.20	$93.20
Purchase #5	$247.58	6.576%	$263.8609	$263.86	$263.85	$263.90
Purchase #6	$142.31	8.169%	$153.9353	$153.94	$153.95	$153.90
Purchase #7	$213.83	3.502%	$221.3183	$221.32	$221.30	$221.30
7 purchase totals =	$1,172.83		$1,259.4078	$1,259.42	$1,259.40	$1,259.40