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	$185.88	9.500%	$203.5386	$203.54	$203.55	$203.50
Purchase #2	$159.62	4.222%	$166.3592	$166.36	$166.35	$166.40
Purchase #3	$75.71	3.654%	$78.4764	$78.48	$78.50	$78.50
Purchase #4	$140.77	12.237%	$157.996	$158.00	$158.00	$158.00
Purchase #5	$174.92	7.681%	$188.3556	$188.36	$188.35	$188.40
Purchase #6	$156.81	6.114%	$166.3974	$166.40	$166.40	$166.40
Purchase #7	$68.74	13.728%	$78.1766	$78.18	$78.20	$78.20
7 purchase totals =	$962.45		$1,039.2998	$1,039.32	$1,039.35	$1,039.40