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	$132.71	13.421%	$150.521	$150.52	$150.50	$150.50
Purchase #2	$52.62	13.711%	$59.8347	$59.83	$59.85	$59.80
Purchase #3	$88.86	8.333%	$96.2647	$96.26	$96.25	$96.30
Purchase #4	$114.84	4.402%	$119.8953	$119.90	$119.90	$119.90
Purchase #5	$155.40	6.790%	$165.9517	$165.95	$165.95	$166.00
Purchase #6	$173.94	8.430%	$188.6031	$188.60	$188.60	$188.60
Purchase #7	$87.70	3.333%	$90.623	$90.62	$90.60	$90.60
7 purchase totals =	$806.07		$871.6935	$871.68	$871.65	$871.70