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	$76.25	12.728%	$85.9551	$85.96	$85.95	$86.00
Purchase #2	$39.94	13.784%	$45.4453	$45.45	$45.45	$45.40
Purchase #3	$133.74	10.293%	$147.5059	$147.51	$147.50	$147.50
Purchase #4	$245.74	4.615%	$257.0809	$257.08	$257.10	$257.10
Purchase #5	$163.86	4.830%	$171.7744	$171.77	$171.75	$171.80
Purchase #6	$142.47	4.162%	$148.3996	$148.40	$148.40	$148.40
Purchase #7	$37.33	3.650%	$38.6925	$38.69	$38.70	$38.70
7 purchase totals =	$839.33		$894.8537	$894.86	$894.85	$894.90