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	$129.40	6.346%	$137.6117	$137.61	$137.60	$137.60
Purchase #2	$69.46	4.800%	$72.7941	$72.79	$72.80	$72.80
Purchase #3	$88.98	3.155%	$91.7873	$91.79	$91.80	$91.80
Purchase #4	$13.31	10.171%	$14.6638	$14.66	$14.65	$14.70
Purchase #5	$173.26	6.122%	$183.867	$183.87	$183.85	$183.90
Purchase #6	$139.86	4.364%	$145.9635	$145.96	$145.95	$146.00
Purchase #7	$220.78	8.180%	$238.8398	$238.84	$238.85	$238.80
7 purchase totals =	$835.05		$885.5272	$885.52	$885.50	$885.60