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	$77.64	13.173%	$87.8675	$87.87	$87.85	$87.90
Purchase #2	$248.73	10.492%	$274.8268	$274.83	$274.85	$274.80
Purchase #3	$91.29	13.837%	$103.9218	$103.92	$103.90	$103.90
Purchase #4	$114.76	5.264%	$120.801	$120.80	$120.80	$120.80
Purchase #5	$230.66	8.643%	$250.5959	$250.60	$250.60	$250.60
Purchase #6	$98.99	12.417%	$111.2816	$111.28	$111.30	$111.30
Purchase #7	$49.76	7.601%	$53.5423	$53.54	$53.55	$53.50
7 purchase totals =	$911.83		$1,002.8369	$1,002.84	$1,002.85	$1,002.80