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	$200.58	6.819%	$214.2576	$214.26	$214.25	$214.30
Purchase #2	$131.73	9.175%	$143.8162	$143.82	$143.80	$143.80
Purchase #3	$230.45	3.279%	$238.0065	$238.01	$238.00	$238.00
Purchase #4	$106.89	3.543%	$110.6771	$110.68	$110.70	$110.70
Purchase #5	$51.50	10.395%	$56.8534	$56.85	$56.85	$56.90
Purchase #6	$116.46	10.437%	$128.6149	$128.61	$128.60	$128.60
Purchase #7	$149.80	11.640%	$167.2367	$167.24	$167.25	$167.20
7 purchase totals =	$987.41		$1,059.4624	$1,059.47	$1,059.45	$1,059.50