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	$158.38	6.648%	$168.9091	$168.91	$168.90	$168.90
Purchase #2	$32.64	8.242%	$35.3302	$35.33	$35.35	$35.30
Purchase #3	$225.95	10.286%	$249.1912	$249.19	$249.20	$249.20
Purchase #4	$145.83	7.488%	$156.7498	$156.75	$156.75	$156.70
Purchase #5	$78.29	12.143%	$87.7968	$87.80	$87.80	$87.80
Purchase #6	$184.94	12.323%	$207.7302	$207.73	$207.75	$207.70
Purchase #7	$143.87	8.151%	$155.5968	$155.60	$155.60	$155.60
7 purchase totals =	$969.90		$1,061.3041	$1,061.31	$1,061.35	$1,061.20