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	$105.99	7.473%	$113.9106	$113.91	$113.90	$113.90
Purchase #2	$77.71	5.224%	$81.7696	$81.77	$81.75	$81.80
Purchase #3	$93.40	7.477%	$100.3835	$100.38	$100.40	$100.40
Purchase #4	$165.65	10.429%	$182.9256	$182.93	$182.95	$182.90
Purchase #5	$136.37	3.834%	$141.5984	$141.60	$141.60	$141.60
Purchase #6	$55.55	3.478%	$57.482	$57.48	$57.50	$57.50
Purchase #7	$114.78	3.753%	$119.0877	$119.09	$119.10	$119.10
7 purchase totals =	$749.45		$797.1574	$797.16	$797.20	$797.20