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	$107.97	6.817%	$115.3303	$115.33	$115.35	$115.30
Purchase #2	$100.84	8.851%	$109.7653	$109.77	$109.75	$109.80
Purchase #3	$235.66	6.760%	$251.5906	$251.59	$251.60	$251.60
Purchase #4	$118.93	11.311%	$132.3822	$132.38	$132.40	$132.40
Purchase #5	$166.59	3.682%	$172.7238	$172.72	$172.70	$172.70
Purchase #6	$40.60	12.621%	$45.7241	$45.72	$45.70	$45.70
Purchase #7	$41.32	9.734%	$45.3421	$45.34	$45.35	$45.30
7 purchase totals =	$811.91		$872.8584	$872.85	$872.85	$872.80