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	$146.98	11.765%	$164.2722	$164.27	$164.25	$164.30
Purchase #2	$96.77	3.855%	$100.5005	$100.50	$100.50	$100.50
Purchase #3	$53.77	5.603%	$56.7827	$56.78	$56.80	$56.80
Purchase #4	$70.40	3.361%	$72.7661	$72.77	$72.75	$72.80
Purchase #5	$105.95	7.456%	$113.8496	$113.85	$113.85	$113.80
Purchase #6	$82.75	13.241%	$93.7069	$93.71	$93.70	$93.70
Purchase #7	$76.92	9.293%	$84.0682	$84.07	$84.05	$84.10
7 purchase totals =	$633.54		$685.9462	$685.95	$685.90	$686.00