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	$43.25	6.352%	$45.9972	$46.00	$46.00	$46.00
Purchase #2	$55.78	6.606%	$59.4648	$59.46	$59.45	$59.50
Purchase #3	$125.62	13.769%	$142.9166	$142.92	$142.90	$142.90
Purchase #4	$73.52	8.245%	$79.5817	$79.58	$79.60	$79.60
Purchase #5	$15.68	8.427%	$17.0014	$17.00	$17.00	$17.00
Purchase #6	$207.38	6.696%	$221.2662	$221.27	$221.25	$221.30
Purchase #7	$89.55	10.672%	$99.1068	$99.11	$99.10	$99.10
7 purchase totals =	$610.78		$665.3347	$665.34	$665.30	$665.40