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	$158.89	4.643%	$166.2673	$166.27	$166.25	$166.30
Purchase #2	$95.38	10.414%	$105.3129	$105.31	$105.30	$105.30
Purchase #3	$150.38	4.807%	$157.6088	$157.61	$157.60	$157.60
Purchase #4	$29.26	10.471%	$32.3238	$32.32	$32.30	$32.30
Purchase #5	$99.49	4.779%	$104.2446	$104.24	$104.25	$104.20
Purchase #6	$69.73	8.820%	$75.8802	$75.88	$75.90	$75.90
Purchase #7	$176.90	7.803%	$190.7035	$190.70	$190.70	$190.70
7 purchase totals =	$780.03		$832.3411	$832.33	$832.30	$832.30