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	$120.90	7.570%	$130.0521	$130.05	$130.05	$130.10
Purchase #2	$112.32	3.154%	$115.8626	$115.86	$115.85	$115.90
Purchase #3	$117.55	4.769%	$123.156	$123.16	$123.15	$123.20
Purchase #4	$35.64	5.419%	$37.5713	$37.57	$37.55	$37.60
Purchase #5	$121.28	4.241%	$126.4235	$126.42	$126.40	$126.40
Purchase #6	$15.43	12.752%	$17.3976	$17.40	$17.40	$17.40
Purchase #7	$59.83	4.314%	$62.4111	$62.41	$62.40	$62.40
7 purchase totals =	$582.95		$612.8742	$612.87	$612.80	$613.00