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	$169.69	9.355%	$185.5645	$185.56	$185.55	$185.60
Purchase #2	$137.76	5.159%	$144.867	$144.87	$144.85	$144.90
Purchase #3	$225.95	7.145%	$242.0941	$242.09	$242.10	$242.10
Purchase #4	$146.69	10.397%	$161.9414	$161.94	$161.95	$161.90
Purchase #5	$161.84	7.761%	$174.4004	$174.40	$174.40	$174.40
Purchase #6	$76.78	13.171%	$86.8927	$86.89	$86.90	$86.90
Purchase #7	$238.59	7.244%	$255.8735	$255.87	$255.85	$255.90
7 purchase totals =	$1,157.30		$1,251.6336	$1,251.62	$1,251.60	$1,251.70