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	$161.47	4.824%	$169.2593	$169.26	$169.25	$169.30
Purchase #2	$89.92	10.779%	$99.6125	$99.61	$99.60	$99.60
Purchase #3	$184.40	4.622%	$192.923	$192.92	$192.90	$192.90
Purchase #4	$195.66	4.691%	$204.8384	$204.84	$204.85	$204.80
Purchase #5	$227.67	7.765%	$245.3486	$245.35	$245.35	$245.30
Purchase #6	$93.40	7.299%	$100.2173	$100.22	$100.20	$100.20
Purchase #7	$74.71	5.433%	$78.769	$78.77	$78.75	$78.80
7 purchase totals =	$1,027.23		$1,090.9681	$1,090.97	$1,090.90	$1,090.90