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	$71.41	12.442%	$80.2948	$80.29	$80.30	$80.30
Purchase #2	$6.57	12.590%	$7.3972	$7.40	$7.40	$7.40
Purchase #3	$207.66	4.266%	$216.5188	$216.52	$216.50	$216.50
Purchase #4	$116.78	5.622%	$123.3454	$123.35	$123.35	$123.30
Purchase #5	$216.48	12.262%	$243.0248	$243.02	$243.00	$243.00
Purchase #6	$218.38	8.804%	$237.6062	$237.61	$237.60	$237.60
Purchase #7	$119.88	6.733%	$127.9515	$127.95	$127.95	$128.00
7 purchase totals =	$957.16		$1,036.1387	$1,036.14	$1,036.10	$1,036.10