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	$210.37	12.564%	$236.8009	$236.80	$236.80	$236.80
Purchase #2	$80.29	13.205%	$90.8923	$90.89	$90.90	$90.90
Purchase #3	$114.38	12.445%	$128.6146	$128.61	$128.60	$128.60
Purchase #4	$55.46	5.605%	$58.5685	$58.57	$58.55	$58.60
Purchase #5	$130.81	9.833%	$143.6725	$143.67	$143.65	$143.70
Purchase #6	$135.91	12.697%	$153.1665	$153.17	$153.15	$153.20
Purchase #7	$245.92	5.529%	$259.5169	$259.52	$259.50	$259.50
7 purchase totals =	$973.14		$1,071.2322	$1,071.23	$1,071.15	$1,071.30