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	$31.75	7.262%	$34.0557	$34.06	$34.05	$34.10
Purchase #2	$182.43	4.213%	$190.1158	$190.12	$190.10	$190.10
Purchase #3	$78.52	13.420%	$89.0574	$89.06	$89.05	$89.10
Purchase #4	$243.98	5.725%	$257.9479	$257.95	$257.95	$257.90
Purchase #5	$56.83	8.761%	$61.8089	$61.81	$61.80	$61.80
Purchase #6	$147.59	10.188%	$162.6265	$162.63	$162.65	$162.60
Purchase #7	$222.82	5.647%	$235.4026	$235.40	$235.40	$235.40
7 purchase totals =	$963.92		$1,031.0148	$1,031.03	$1,031.00	$1,031.00