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	$217.56	9.579%	$238.4001	$238.40	$238.40	$238.40
Purchase #2	$66.76	13.627%	$75.8574	$75.86	$75.85	$75.90
Purchase #3	$184.76	6.173%	$196.1652	$196.17	$196.15	$196.20
Purchase #4	$165.70	3.269%	$171.1167	$171.12	$171.10	$171.10
Purchase #5	$161.27	9.691%	$176.8987	$176.90	$176.90	$176.90
Purchase #6	$29.45	8.833%	$32.0513	$32.05	$32.05	$32.10
Purchase #7	$216.63	11.317%	$241.146	$241.15	$241.15	$241.10
7 purchase totals =	$1,042.13		$1,131.6354	$1,131.65	$1,131.60	$1,131.70