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	$59.90	13.367%	$67.9068	$67.91	$67.90	$67.90
Purchase #2	$108.78	13.586%	$123.5589	$123.56	$123.55	$123.60
Purchase #3	$162.57	7.497%	$174.7579	$174.76	$174.75	$174.80
Purchase #4	$200.25	9.202%	$218.677	$218.68	$218.70	$218.70
Purchase #5	$190.64	10.353%	$210.377	$210.38	$210.40	$210.40
Purchase #6	$188.63	6.162%	$200.2534	$200.25	$200.25	$200.30
Purchase #7	$239.78	5.276%	$252.4308	$252.43	$252.45	$252.40
7 purchase totals =	$1,150.55		$1,247.9618	$1,247.97	$1,248.00	$1,248.10