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	$121.45	7.731%	$130.8393	$130.84	$130.85	$130.80
Purchase #2	$56.39	13.237%	$63.8543	$63.85	$63.85	$63.90
Purchase #3	$161.40	6.566%	$171.9975	$172.00	$172.00	$172.00
Purchase #4	$69.32	4.712%	$72.5864	$72.59	$72.60	$72.60
Purchase #5	$95.55	12.159%	$107.1679	$107.17	$107.15	$107.20
Purchase #6	$141.92	7.331%	$152.3242	$152.32	$152.30	$152.30
Purchase #7	$222.25	12.778%	$250.6491	$250.65	$250.65	$250.60
7 purchase totals =	$868.28		$949.4187	$949.42	$949.40	$949.40