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	$89.75	3.314%	$92.7243	$92.72	$92.70	$92.70
Purchase #2	$27.35	8.856%	$29.7721	$29.77	$29.75	$29.80
Purchase #3	$82.56	8.418%	$89.5099	$89.51	$89.50	$89.50
Purchase #4	$18.95	13.688%	$21.5439	$21.54	$21.55	$21.50
Purchase #5	$144.87	8.841%	$157.678	$157.68	$157.70	$157.70
Purchase #6	$99.84	3.370%	$103.2046	$103.20	$103.20	$103.20
Purchase #7	$100.99	8.246%	$109.3176	$109.32	$109.30	$109.30
7 purchase totals =	$564.31		$603.7504	$603.74	$603.70	$603.70