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	$227.36	10.364%	$250.9236	$250.92	$250.90	$250.90
Purchase #2	$156.31	8.207%	$169.1384	$169.14	$169.15	$169.10
Purchase #3	$156.89	13.495%	$178.0623	$178.06	$178.05	$178.10
Purchase #4	$29.40	4.159%	$30.6227	$30.62	$30.60	$30.60
Purchase #5	$113.25	5.776%	$119.7913	$119.79	$119.80	$119.80
Purchase #6	$158.53	8.656%	$172.2524	$172.25	$172.25	$172.30
Purchase #7	$122.72	6.812%	$131.0797	$131.08	$131.10	$131.10
7 purchase totals =	$964.46		$1,051.8704	$1,051.86	$1,051.85	$1,051.90