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	$115.65	9.281%	$126.3835	$126.38	$126.40	$126.40
Purchase #2	$168.59	8.202%	$182.4178	$182.42	$182.40	$182.40
Purchase #3	$142.67	6.674%	$152.1918	$152.19	$152.20	$152.20
Purchase #4	$108.25	3.213%	$111.7281	$111.73	$111.75	$111.70
Purchase #5	$20.74	4.192%	$21.6094	$21.61	$21.60	$21.60
Purchase #6	$72.99	6.782%	$77.9402	$77.94	$77.95	$77.90
Purchase #7	$160.40	11.752%	$179.2502	$179.25	$179.25	$179.30
7 purchase totals =	$789.29		$851.5210	$851.52	$851.55	$851.50