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	$59.45	3.302%	$61.413	$61.41	$61.40	$61.40
Purchase #2	$51.52	10.772%	$57.0697	$57.07	$57.05	$57.10
Purchase #3	$229.51	13.741%	$261.047	$261.05	$261.05	$261.00
Purchase #4	$74.53	10.728%	$82.5256	$82.53	$82.55	$82.50
Purchase #5	$111.53	10.870%	$123.6533	$123.65	$123.65	$123.70
Purchase #6	$5.60	9.649%	$6.1403	$6.14	$6.15	$6.10
Purchase #7	$247.59	5.160%	$260.3656	$260.37	$260.35	$260.40
7 purchase totals =	$779.73		$852.2145	$852.22	$852.20	$852.20