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	$151.64	9.637%	$166.2535	$166.25	$166.25	$166.30
Purchase #2	$50.95	10.410%	$56.2539	$56.25	$56.25	$56.30
Purchase #3	$216.59	6.673%	$231.0431	$231.04	$231.05	$231.00
Purchase #4	$56.78	9.164%	$61.9833	$61.98	$62.00	$62.00
Purchase #5	$102.60	11.464%	$114.3621	$114.36	$114.35	$114.40
Purchase #6	$9.56	7.232%	$10.2514	$10.25	$10.25	$10.30
Purchase #7	$231.66	10.613%	$256.2461	$256.25	$256.25	$256.20
7 purchase totals =	$819.78		$896.3934	$896.38	$896.40	$896.50