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	$212.58	4.642%	$222.448	$222.45	$222.45	$222.40
Purchase #2	$116.47	10.165%	$128.3092	$128.31	$128.30	$128.30
Purchase #3	$111.58	9.684%	$122.3854	$122.39	$122.40	$122.40
Purchase #4	$158.33	7.305%	$169.896	$169.90	$169.90	$169.90
Purchase #5	$196.33	5.403%	$206.9377	$206.94	$206.95	$206.90
Purchase #6	$205.74	10.657%	$227.6657	$227.67	$227.65	$227.70
Purchase #7	$65.73	10.396%	$72.5633	$72.56	$72.55	$72.60
7 purchase totals =	$1,066.76		$1,150.2053	$1,150.22	$1,150.20	$1,150.20