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	$35.92	4.295%	$37.4628	$37.46	$37.45	$37.50
Purchase #2	$138.88	8.262%	$150.3543	$150.35	$150.35	$150.40
Purchase #3	$64.92	9.184%	$70.8823	$70.88	$70.90	$70.90
Purchase #4	$240.43	13.268%	$272.3303	$272.33	$272.35	$272.30
Purchase #5	$121.41	3.784%	$126.0042	$126.00	$126.00	$126.00
Purchase #6	$168.78	6.384%	$179.5549	$179.55	$179.55	$179.60
Purchase #7	$91.65	13.211%	$103.7579	$103.76	$103.75	$103.80
7 purchase totals =	$861.99		$940.3467	$940.33	$940.35	$940.50