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	$49.30	6.218%	$52.3655	$52.37	$52.35	$52.40
Purchase #2	$138.67	12.503%	$156.0079	$156.01	$156.00	$156.00
Purchase #3	$83.39	7.255%	$89.4399	$89.44	$89.45	$89.40
Purchase #4	$158.37	8.505%	$171.8394	$171.84	$171.85	$171.80
Purchase #5	$147.72	6.467%	$157.2731	$157.27	$157.25	$157.30
Purchase #6	$84.29	6.559%	$89.8186	$89.82	$89.80	$89.80
Purchase #7	$15.88	5.431%	$16.7424	$16.74	$16.75	$16.70
7 purchase totals =	$677.62		$733.4868	$733.49	$733.45	$733.40