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	$148.94	13.840%	$169.5533	$169.55	$169.55	$169.60
Purchase #2	$208.51	4.470%	$217.8304	$217.83	$217.85	$217.80
Purchase #3	$228.44	4.605%	$238.9597	$238.96	$238.95	$239.00
Purchase #4	$44.77	3.386%	$46.2859	$46.29	$46.30	$46.30
Purchase #5	$70.91	13.510%	$80.4899	$80.49	$80.50	$80.50
Purchase #6	$178.92	3.790%	$185.7011	$185.70	$185.70	$185.70
Purchase #7	$180.57	13.700%	$205.3081	$205.31	$205.30	$205.30
7 purchase totals =	$1,061.06		$1,144.1284	$1,144.13	$1,144.15	$1,144.20