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	$186.94	13.842%	$212.8162	$212.82	$212.80	$212.80
Purchase #2	$55.86	5.709%	$59.049	$59.05	$59.05	$59.00
Purchase #3	$168.71	4.847%	$176.8874	$176.89	$176.90	$176.90
Purchase #4	$85.87	5.401%	$90.5078	$90.51	$90.50	$90.50
Purchase #5	$169.52	12.217%	$190.2303	$190.23	$190.25	$190.20
Purchase #6	$55.92	6.219%	$59.3977	$59.40	$59.40	$59.40
Purchase #7	$150.75	5.352%	$158.8181	$158.82	$158.80	$158.80
7 purchase totals =	$873.57		$947.7065	$947.72	$947.70	$947.60