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	$229.85	10.194%	$253.2809	$253.28	$253.30	$253.30
Purchase #2	$188.30	6.371%	$200.2966	$200.30	$200.30	$200.30
Purchase #3	$130.29	5.481%	$137.4312	$137.43	$137.45	$137.40
Purchase #4	$62.80	3.635%	$65.0828	$65.08	$65.10	$65.10
Purchase #5	$131.41	7.744%	$141.5864	$141.59	$141.60	$141.60
Purchase #6	$83.51	10.686%	$92.4339	$92.43	$92.45	$92.40
Purchase #7	$76.78	6.699%	$81.9235	$81.92	$81.90	$81.90
7 purchase totals =	$902.94		$972.0353	$972.03	$972.10	$972.00