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	$88.33	9.321%	$96.5632	$96.56	$96.55	$96.60
Purchase #2	$205.60	8.840%	$223.775	$223.78	$223.80	$223.80
Purchase #3	$100.55	4.113%	$104.6856	$104.69	$104.70	$104.70
Purchase #4	$61.58	3.596%	$63.7944	$63.79	$63.80	$63.80
Purchase #5	$37.81	9.543%	$41.4182	$41.42	$41.40	$41.40
Purchase #6	$52.34	4.246%	$54.5624	$54.56	$54.55	$54.60
Purchase #7	$31.63	7.769%	$34.0873	$34.09	$34.10	$34.10
7 purchase totals =	$577.84		$618.8861	$618.89	$618.90	$619.00