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	$212.91	9.466%	$233.0641	$233.06	$233.05	$233.10
Purchase #2	$138.83	4.286%	$144.7803	$144.78	$144.80	$144.80
Purchase #3	$199.37	13.193%	$225.6729	$225.67	$225.65	$225.70
Purchase #4	$226.36	8.173%	$244.8604	$244.86	$244.85	$244.90
Purchase #5	$85.89	3.577%	$88.9623	$88.96	$88.95	$89.00
Purchase #6	$106.92	5.805%	$113.1267	$113.13	$113.15	$113.10
Purchase #7	$109.32	8.301%	$118.3947	$118.39	$118.40	$118.40
7 purchase totals =	$1,079.60		$1,168.8614	$1,168.85	$1,168.85	$1,169.00