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	$109.31	3.404%	$113.0309	$113.03	$113.05	$113.00
Purchase #2	$171.25	5.191%	$180.1396	$180.14	$180.15	$180.10
Purchase #3	$103.39	10.332%	$114.0723	$114.07	$114.05	$114.10
Purchase #4	$111.69	4.693%	$116.9316	$116.93	$116.95	$116.90
Purchase #5	$127.76	9.691%	$140.1412	$140.14	$140.15	$140.10
Purchase #6	$195.79	4.250%	$204.1111	$204.11	$204.10	$204.10
Purchase #7	$101.50	13.230%	$114.9285	$114.93	$114.95	$114.90
7 purchase totals =	$920.69		$983.3552	$983.35	$983.40	$983.20