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	$178.79	3.143%	$184.4094	$184.41	$184.40	$184.40
Purchase #2	$116.61	5.815%	$123.3909	$123.39	$123.40	$123.40
Purchase #3	$103.53	7.271%	$111.0577	$111.06	$111.05	$111.10
Purchase #4	$66.30	8.688%	$72.0601	$72.06	$72.05	$72.10
Purchase #5	$192.97	12.559%	$217.2051	$217.21	$217.20	$217.20
Purchase #6	$194.52	12.607%	$219.0431	$219.04	$219.05	$219.00
Purchase #7	$188.87	6.649%	$201.428	$201.43	$201.45	$201.40
7 purchase totals =	$1,041.59		$1,128.5943	$1,128.60	$1,128.60	$1,128.60