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	$140.89	6.599%	$150.1873	$150.19	$150.20	$150.20
Purchase #2	$222.33	10.302%	$245.2344	$245.23	$245.25	$245.20
Purchase #3	$168.49	13.660%	$191.5057	$191.51	$191.50	$191.50
Purchase #4	$42.52	10.116%	$46.8213	$46.82	$46.80	$46.80
Purchase #5	$218.68	10.432%	$241.4927	$241.49	$241.50	$241.50
Purchase #6	$242.69	3.639%	$251.5215	$251.52	$251.50	$251.50
Purchase #7	$60.83	8.254%	$65.8509	$65.85	$65.85	$65.90
7 purchase totals =	$1,096.43		$1,192.6138	$1,192.61	$1,192.60	$1,192.60