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	$168.40	13.126%	$190.5042	$190.50	$190.50	$190.50
Purchase #2	$97.83	10.423%	$108.0268	$108.03	$108.05	$108.00
Purchase #3	$162.81	3.274%	$168.1404	$168.14	$168.15	$168.10
Purchase #4	$243.77	3.136%	$251.4146	$251.41	$251.40	$251.40
Purchase #5	$236.47	3.353%	$244.3988	$244.40	$244.40	$244.40
Purchase #6	$113.72	4.556%	$118.9011	$118.90	$118.90	$118.90
Purchase #7	$154.38	4.200%	$160.864	$160.86	$160.85	$160.90
7 purchase totals =	$1,177.38		$1,242.2499	$1,242.24	$1,242.25	$1,242.20