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	$191.87	8.853%	$208.8563	$208.86	$208.85	$208.90
Purchase #2	$174.40	6.408%	$185.5756	$185.58	$185.60	$185.60
Purchase #3	$197.39	13.317%	$223.6764	$223.68	$223.70	$223.70
Purchase #4	$141.64	6.345%	$150.6271	$150.63	$150.65	$150.60
Purchase #5	$38.70	10.510%	$42.7674	$42.77	$42.75	$42.80
Purchase #6	$108.81	9.746%	$119.4146	$119.41	$119.40	$119.40
Purchase #7	$77.45	5.585%	$81.7756	$81.78	$81.80	$81.80
7 purchase totals =	$930.26		$1,012.6930	$1,012.71	$1,012.75	$1,012.80