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	$81.85	10.401%	$90.3632	$90.36	$90.35	$90.40
Purchase #2	$17.29	10.590%	$19.121	$19.12	$19.10	$19.10
Purchase #3	$233.45	4.831%	$244.728	$244.73	$244.75	$244.70
Purchase #4	$40.54	12.454%	$45.5889	$45.59	$45.60	$45.60
Purchase #5	$106.96	10.293%	$117.9694	$117.97	$117.95	$118.00
Purchase #6	$231.33	4.355%	$241.4044	$241.40	$241.40	$241.40
Purchase #7	$112.48	5.311%	$118.4538	$118.45	$118.45	$118.50
7 purchase totals =	$823.90		$877.6287	$877.62	$877.60	$877.70