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	$235.83	4.561%	$246.5862	$246.59	$246.60	$246.60
Purchase #2	$118.91	9.565%	$130.2837	$130.28	$130.30	$130.30
Purchase #3	$81.45	11.449%	$90.7752	$90.78	$90.80	$90.80
Purchase #4	$164.47	6.387%	$174.9747	$174.97	$174.95	$175.00
Purchase #5	$206.54	4.268%	$215.3551	$215.36	$215.35	$215.40
Purchase #6	$92.93	8.402%	$100.738	$100.74	$100.75	$100.70
Purchase #7	$112.77	12.874%	$127.288	$127.29	$127.30	$127.30
7 purchase totals =	$1,012.90		$1,086.0009	$1,086.01	$1,086.05	$1,086.10