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	$166.68	11.122%	$185.2181	$185.22	$185.20	$185.20
Purchase #2	$81.68	6.270%	$86.8013	$86.80	$86.80	$86.80
Purchase #3	$86.27	5.312%	$90.8527	$90.85	$90.85	$90.90
Purchase #4	$176.58	7.272%	$189.4209	$189.42	$189.40	$189.40
Purchase #5	$86.25	9.390%	$94.3489	$94.35	$94.35	$94.30
Purchase #6	$207.67	11.673%	$231.9113	$231.91	$231.90	$231.90
Purchase #7	$60.56	7.553%	$65.1341	$65.13	$65.15	$65.10
7 purchase totals =	$865.69		$943.6873	$943.68	$943.65	$943.60