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	$52.72	13.564%	$59.8709	$59.87	$59.85	$59.90
Purchase #2	$38.32	4.803%	$40.1605	$40.16	$40.15	$40.20
Purchase #3	$232.66	4.502%	$243.1344	$243.13	$243.15	$243.10
Purchase #4	$128.84	8.270%	$139.4951	$139.50	$139.50	$139.50
Purchase #5	$140.61	10.589%	$155.4992	$155.50	$155.50	$155.50
Purchase #6	$207.77	7.427%	$223.2011	$223.20	$223.20	$223.20
Purchase #7	$188.65	13.573%	$214.2555	$214.26	$214.25	$214.30
7 purchase totals =	$989.57		$1,075.6167	$1,075.62	$1,075.60	$1,075.70