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	$142.44	5.210%	$149.8611	$149.86	$149.85	$149.90
Purchase #2	$5.86	12.573%	$6.5968	$6.60	$6.60	$6.60
Purchase #3	$100.87	10.478%	$111.4392	$111.44	$111.45	$111.40
Purchase #4	$138.92	5.498%	$146.5578	$146.56	$146.55	$146.60
Purchase #5	$177.27	12.323%	$199.115	$199.12	$199.10	$199.10
Purchase #6	$210.76	3.566%	$218.2757	$218.28	$218.30	$218.30
Purchase #7	$125.58	4.762%	$131.5601	$131.56	$131.55	$131.60
7 purchase totals =	$901.70		$963.4057	$963.42	$963.40	$963.50