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	$140.44	9.629%	$153.963	$153.96	$153.95	$154.00
Purchase #2	$229.72	10.833%	$254.6056	$254.61	$254.60	$254.60
Purchase #3	$241.28	6.378%	$256.6688	$256.67	$256.65	$256.70
Purchase #4	$60.90	8.110%	$65.839	$65.84	$65.85	$65.80
Purchase #5	$33.35	8.116%	$36.0567	$36.06	$36.05	$36.10
Purchase #6	$243.63	12.586%	$274.2933	$274.29	$274.30	$274.30
Purchase #7	$99.50	11.819%	$111.2599	$111.26	$111.25	$111.30
7 purchase totals =	$1,048.82		$1,152.6863	$1,152.69	$1,152.65	$1,152.80