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	$142.53	4.868%	$149.4684	$149.47	$149.45	$149.50
Purchase #2	$82.77	4.633%	$86.6047	$86.60	$86.60	$86.60
Purchase #3	$129.59	11.338%	$144.2829	$144.28	$144.30	$144.30
Purchase #4	$117.54	12.243%	$131.9304	$131.93	$131.95	$131.90
Purchase #5	$46.35	12.793%	$52.2796	$52.28	$52.30	$52.30
Purchase #6	$19.69	5.806%	$20.8332	$20.83	$20.85	$20.80
Purchase #7	$210.48	8.199%	$227.7373	$227.74	$227.75	$227.70
7 purchase totals =	$748.95		$813.1365	$813.13	$813.20	$813.10