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	$59.59	6.543%	$63.489	$63.49	$63.50	$63.50
Purchase #2	$214.96	10.112%	$236.6968	$236.70	$236.70	$236.70
Purchase #3	$85.52	5.719%	$90.4109	$90.41	$90.40	$90.40
Purchase #4	$143.56	10.116%	$158.0825	$158.08	$158.10	$158.10
Purchase #5	$228.52	8.589%	$248.1476	$248.15	$248.15	$248.10
Purchase #6	$159.40	8.352%	$172.7131	$172.71	$172.70	$172.70
Purchase #7	$136.93	10.224%	$150.9297	$150.93	$150.95	$150.90
7 purchase totals =	$1,028.48		$1,120.4696	$1,120.47	$1,120.50	$1,120.40