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	$11.31	4.604%	$11.8307	$11.83	$11.85	$11.80
Purchase #2	$84.60	9.171%	$92.3587	$92.36	$92.35	$92.40
Purchase #3	$69.43	3.444%	$71.8212	$71.82	$71.80	$71.80
Purchase #4	$222.85	11.313%	$248.061	$248.06	$248.05	$248.10
Purchase #5	$167.67	10.472%	$185.2284	$185.23	$185.25	$185.20
Purchase #6	$176.54	3.161%	$182.1204	$182.12	$182.10	$182.10
Purchase #7	$90.64	3.277%	$93.6103	$93.61	$93.60	$93.60
7 purchase totals =	$823.04		$885.0307	$885.03	$885.00	$885.00