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	$131.31	9.169%	$143.3498	$143.35	$143.35	$143.30
Purchase #2	$36.40	7.392%	$39.0907	$39.09	$39.10	$39.10
Purchase #3	$145.98	5.570%	$154.1111	$154.11	$154.10	$154.10
Purchase #4	$61.95	6.529%	$65.9947	$65.99	$66.00	$66.00
Purchase #5	$81.30	9.636%	$89.1341	$89.13	$89.15	$89.10
Purchase #6	$242.62	5.538%	$256.0563	$256.06	$256.05	$256.10
Purchase #7	$29.79	10.461%	$32.9063	$32.91	$32.90	$32.90
7 purchase totals =	$729.35		$780.6430	$780.64	$780.65	$780.60