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	$106.97	8.764%	$116.3449	$116.34	$116.35	$116.30
Purchase #2	$172.45	13.732%	$196.1308	$196.13	$196.15	$196.10
Purchase #3	$79.26	9.501%	$86.7905	$86.79	$86.80	$86.80
Purchase #4	$172.86	11.254%	$192.3137	$192.31	$192.30	$192.30
Purchase #5	$86.68	7.796%	$93.4376	$93.44	$93.45	$93.40
Purchase #6	$175.62	9.545%	$192.3829	$192.38	$192.40	$192.40
Purchase #7	$90.68	11.440%	$101.0538	$101.05	$101.05	$101.10
7 purchase totals =	$884.52		$978.4542	$978.44	$978.50	$978.40