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	$147.43	7.380%	$158.3103	$158.31	$158.30	$158.30
Purchase #2	$101.91	8.368%	$110.4378	$110.44	$110.45	$110.40
Purchase #3	$92.48	5.127%	$97.2214	$97.22	$97.20	$97.20
Purchase #4	$55.39	13.578%	$62.9109	$62.91	$62.90	$62.90
Purchase #5	$106.85	4.594%	$111.7587	$111.76	$111.75	$111.80
Purchase #6	$60.94	7.585%	$65.5623	$65.56	$65.55	$65.60
Purchase #7	$78.88	5.818%	$83.4692	$83.47	$83.45	$83.50
7 purchase totals =	$643.88		$689.6706	$689.67	$689.60	$689.70