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	$114.61	12.430%	$128.856	$128.86	$128.85	$128.90
Purchase #2	$202.37	3.527%	$209.5076	$209.51	$209.50	$209.50
Purchase #3	$88.31	12.381%	$99.2437	$99.24	$99.25	$99.20
Purchase #4	$134.35	12.558%	$151.2217	$151.22	$151.20	$151.20
Purchase #5	$161.81	9.323%	$176.8955	$176.90	$176.90	$176.90
Purchase #6	$240.60	5.682%	$254.2709	$254.27	$254.25	$254.30
Purchase #7	$51.35	5.483%	$54.1655	$54.17	$54.15	$54.20
7 purchase totals =	$993.40		$1,074.1609	$1,074.17	$1,074.10	$1,074.20