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	$90.79	12.391%	$102.0398	$102.04	$102.05	$102.00
Purchase #2	$89.93	11.697%	$100.4491	$100.45	$100.45	$100.40
Purchase #3	$100.25	11.708%	$111.9873	$111.99	$112.00	$112.00
Purchase #4	$217.92	3.818%	$226.2402	$226.24	$226.25	$226.20
Purchase #5	$158.87	12.343%	$178.4793	$178.48	$178.50	$178.50
Purchase #6	$196.68	11.549%	$219.3946	$219.39	$219.40	$219.40
Purchase #7	$119.38	7.131%	$127.893	$127.89	$127.90	$127.90
7 purchase totals =	$973.82		$1,066.4833	$1,066.48	$1,066.55	$1,066.40