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	$78.37	10.297%	$86.4398	$86.44	$86.45	$86.40
Purchase #2	$63.67	5.740%	$67.3247	$67.32	$67.30	$67.30
Purchase #3	$96.66	4.280%	$100.797	$100.80	$100.80	$100.80
Purchase #4	$56.60	3.388%	$58.5176	$58.52	$58.50	$58.50
Purchase #5	$78.37	9.806%	$86.055	$86.06	$86.05	$86.10
Purchase #6	$112.70	9.670%	$123.5981	$123.60	$123.60	$123.60
Purchase #7	$137.42	11.137%	$152.7245	$152.72	$152.70	$152.70
7 purchase totals =	$623.79		$675.4567	$675.46	$675.40	$675.40