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	$101.65	3.806%	$105.5188	$105.52	$105.50	$105.50
Purchase #2	$72.88	4.635%	$76.258	$76.26	$76.25	$76.30
Purchase #3	$229.92	10.105%	$253.1534	$253.15	$253.15	$253.20
Purchase #4	$131.69	7.481%	$141.5417	$141.54	$141.55	$141.50
Purchase #5	$32.96	6.528%	$35.1116	$35.11	$35.10	$35.10
Purchase #6	$84.80	13.651%	$96.376	$96.38	$96.40	$96.40
Purchase #7	$31.49	13.748%	$35.8192	$35.82	$35.80	$35.80
7 purchase totals =	$685.39		$743.7787	$743.78	$743.75	$743.80