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	$250.65	4.219%	$261.2249	$261.22	$261.20	$261.20
Purchase #2	$74.99	3.584%	$77.6776	$77.68	$77.70	$77.70
Purchase #3	$40.53	9.675%	$44.4513	$44.45	$44.45	$44.50
Purchase #4	$63.34	12.816%	$71.4577	$71.46	$71.45	$71.50
Purchase #5	$250.52	9.246%	$273.6831	$273.68	$273.70	$273.70
Purchase #6	$182.41	4.412%	$190.4579	$190.46	$190.45	$190.50
Purchase #7	$145.53	11.844%	$162.7666	$162.77	$162.75	$162.80
7 purchase totals =	$1,007.97		$1,081.7191	$1,081.72	$1,081.70	$1,081.90