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	$38.29	12.202%	$42.9621	$42.96	$42.95	$43.00
Purchase #2	$77.76	10.711%	$86.0889	$86.09	$86.10	$86.10
Purchase #3	$184.64	6.606%	$196.8373	$196.84	$196.85	$196.80
Purchase #4	$147.53	6.150%	$156.6031	$156.60	$156.60	$156.60
Purchase #5	$107.28	9.232%	$117.1841	$117.18	$117.20	$117.20
Purchase #6	$98.92	4.615%	$103.4852	$103.49	$103.50	$103.50
Purchase #7	$26.38	12.452%	$29.6648	$29.66	$29.65	$29.70
7 purchase totals =	$680.80		$732.8255	$732.82	$732.85	$732.90