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	$89.92	7.504%	$96.6676	$96.67	$96.65	$96.70
Purchase #2	$34.71	3.298%	$35.8547	$35.85	$35.85	$35.90
Purchase #3	$14.66	8.509%	$15.9074	$15.91	$15.90	$15.90
Purchase #4	$68.99	5.439%	$72.7424	$72.74	$72.75	$72.70
Purchase #5	$129.45	5.658%	$136.7743	$136.77	$136.75	$136.80
Purchase #6	$38.87	9.127%	$42.4177	$42.42	$42.40	$42.40
Purchase #7	$136.45	10.616%	$150.9355	$150.94	$150.95	$150.90
7 purchase totals =	$513.05		$551.2996	$551.30	$551.25	$551.30