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	$97.30	12.609%	$109.5686	$109.57	$109.55	$109.60
Purchase #2	$18.76	9.728%	$20.585	$20.59	$20.60	$20.60
Purchase #3	$176.71	8.664%	$192.0202	$192.02	$192.00	$192.00
Purchase #4	$103.59	11.659%	$115.6676	$115.67	$115.65	$115.70
Purchase #5	$193.38	3.210%	$199.5875	$199.59	$199.60	$199.60
Purchase #6	$130.67	13.245%	$147.9772	$147.98	$148.00	$148.00
Purchase #7	$238.64	10.784%	$264.3749	$264.37	$264.35	$264.40
7 purchase totals =	$959.05		$1,049.7810	$1,049.79	$1,049.75	$1,049.90