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	$127.36	7.181%	$136.5057	$136.51	$136.50	$136.50
Purchase #2	$206.25	8.284%	$223.3358	$223.34	$223.35	$223.30
Purchase #3	$198.33	8.475%	$215.1385	$215.14	$215.15	$215.10
Purchase #4	$226.79	8.543%	$246.1647	$246.16	$246.15	$246.20
Purchase #5	$77.47	4.489%	$80.9476	$80.95	$80.95	$80.90
Purchase #6	$12.83	9.644%	$14.0673	$14.07	$14.05	$14.10
Purchase #7	$92.60	8.135%	$100.133	$100.13	$100.15	$100.10
7 purchase totals =	$941.63		$1,016.2926	$1,016.30	$1,016.30	$1,016.20