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	$241.95	9.158%	$264.1078	$264.11	$264.10	$264.10
Purchase #2	$31.59	12.485%	$35.534	$35.53	$35.55	$35.50
Purchase #3	$120.85	5.446%	$127.4315	$127.43	$127.45	$127.40
Purchase #4	$94.98	5.767%	$100.4575	$100.46	$100.45	$100.50
Purchase #5	$30.81	8.521%	$33.4353	$33.44	$33.45	$33.40
Purchase #6	$197.92	10.335%	$218.375	$218.38	$218.40	$218.40
Purchase #7	$106.83	9.516%	$116.9959	$117.00	$117.00	$117.00
7 purchase totals =	$824.93		$896.3370	$896.35	$896.40	$896.30