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	$107.61	3.440%	$111.3118	$111.31	$111.30	$111.30
Purchase #2	$40.38	11.124%	$44.8719	$44.87	$44.85	$44.90
Purchase #3	$21.33	10.792%	$23.6319	$23.63	$23.65	$23.60
Purchase #4	$165.84	4.208%	$172.8185	$172.82	$172.80	$172.80
Purchase #5	$113.93	3.447%	$117.8572	$117.86	$117.85	$117.90
Purchase #6	$201.94	10.458%	$223.0589	$223.06	$223.05	$223.10
Purchase #7	$180.66	10.737%	$200.0575	$200.06	$200.05	$200.10
7 purchase totals =	$831.69		$893.6077	$893.61	$893.55	$893.70