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	$66.25	9.218%	$72.3569	$72.36	$72.35	$72.40
Purchase #2	$250.98	9.823%	$275.6338	$275.63	$275.65	$275.60
Purchase #3	$240.43	9.743%	$263.8551	$263.86	$263.85	$263.90
Purchase #4	$82.35	8.184%	$89.0895	$89.09	$89.10	$89.10
Purchase #5	$15.51	5.238%	$16.3224	$16.32	$16.30	$16.30
Purchase #6	$85.70	10.822%	$94.9745	$94.97	$94.95	$95.00
Purchase #7	$51.78	8.179%	$56.0151	$56.02	$56.00	$56.00
7 purchase totals =	$793.00		$868.2473	$868.25	$868.20	$868.30