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	$224.33	11.484%	$250.0921	$250.09	$250.10	$250.10
Purchase #2	$99.83	11.625%	$111.4352	$111.44	$111.45	$111.40
Purchase #3	$241.79	13.250%	$273.8272	$273.83	$273.85	$273.80
Purchase #4	$234.85	9.842%	$257.9639	$257.96	$257.95	$258.00
Purchase #5	$100.38	6.748%	$107.1536	$107.15	$107.15	$107.20
Purchase #6	$180.45	10.420%	$199.2529	$199.25	$199.25	$199.30
Purchase #7	$92.25	9.774%	$101.2665	$101.27	$101.25	$101.30
7 purchase totals =	$1,173.88		$1,300.9914	$1,300.99	$1,301.00	$1,301.10