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	$122.62	3.407%	$126.7977	$126.80	$126.80	$126.80
Purchase #2	$242.89	10.121%	$267.4729	$267.47	$267.45	$267.50
Purchase #3	$216.72	13.461%	$245.8927	$245.89	$245.90	$245.90
Purchase #4	$31.80	8.711%	$34.5701	$34.57	$34.55	$34.60
Purchase #5	$18.35	11.149%	$20.3958	$20.40	$20.40	$20.40
Purchase #6	$210.90	3.744%	$218.7961	$218.80	$218.80	$218.80
Purchase #7	$99.82	5.699%	$105.5087	$105.51	$105.50	$105.50
7 purchase totals =	$943.10		$1,019.4340	$1,019.44	$1,019.40	$1,019.50