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	$241.35	7.277%	$258.913	$258.91	$258.90	$258.90
Purchase #2	$185.32	13.393%	$210.1399	$210.14	$210.15	$210.10
Purchase #3	$86.83	4.115%	$90.4031	$90.40	$90.40	$90.40
Purchase #4	$58.91	3.369%	$60.8947	$60.89	$60.90	$60.90
Purchase #5	$198.25	12.742%	$223.511	$223.51	$223.50	$223.50
Purchase #6	$231.52	13.150%	$261.9649	$261.96	$261.95	$262.00
Purchase #7	$51.50	6.431%	$54.812	$54.81	$54.80	$54.80
7 purchase totals =	$1,053.68		$1,160.6386	$1,160.62	$1,160.60	$1,160.60