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	$91.83	5.556%	$96.9321	$96.93	$96.95	$96.90
Purchase #2	$249.60	9.331%	$272.8902	$272.89	$272.90	$272.90
Purchase #3	$162.71	9.854%	$178.7434	$178.74	$178.75	$178.70
Purchase #4	$226.37	10.494%	$250.1253	$250.13	$250.15	$250.10
Purchase #5	$38.41	12.664%	$43.2742	$43.27	$43.25	$43.30
Purchase #6	$101.26	4.598%	$105.9159	$105.92	$105.90	$105.90
Purchase #7	$13.52	12.140%	$15.1613	$15.16	$15.15	$15.20
7 purchase totals =	$883.70		$963.0424	$963.04	$963.05	$963.00