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	$56.68	9.343%	$61.9756	$61.98	$62.00	$62.00
Purchase #2	$161.38	11.632%	$180.1517	$180.15	$180.15	$180.20
Purchase #3	$136.26	11.436%	$151.8427	$151.84	$151.85	$151.80
Purchase #4	$152.26	4.594%	$159.2548	$159.25	$159.25	$159.30
Purchase #5	$24.57	9.193%	$26.8287	$26.83	$26.85	$26.80
Purchase #6	$83.77	6.809%	$89.4739	$89.47	$89.45	$89.50
Purchase #7	$67.78	6.635%	$72.2772	$72.28	$72.30	$72.30
7 purchase totals =	$682.70		$741.8046	$741.80	$741.85	$741.90