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	$77.64	6.700%	$82.8419	$82.84	$82.85	$82.80
Purchase #2	$244.81	12.523%	$275.4676	$275.47	$275.45	$275.50
Purchase #3	$188.74	5.302%	$198.747	$198.75	$198.75	$198.70
Purchase #4	$112.45	5.252%	$118.3559	$118.36	$118.35	$118.40
Purchase #5	$127.34	13.746%	$144.8442	$144.84	$144.85	$144.80
Purchase #6	$148.34	7.730%	$159.8067	$159.81	$159.80	$159.80
Purchase #7	$86.74	13.593%	$98.5306	$98.53	$98.55	$98.50
7 purchase totals =	$986.06		$1,078.5939	$1,078.60	$1,078.60	$1,078.50