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	$179.29	6.712%	$191.3239	$191.32	$191.30	$191.30
Purchase #2	$166.62	10.701%	$184.45	$184.45	$184.45	$184.50
Purchase #3	$199.98	4.633%	$209.2451	$209.25	$209.25	$209.20
Purchase #4	$180.76	6.208%	$191.9816	$191.98	$192.00	$192.00
Purchase #5	$128.29	11.555%	$143.1139	$143.11	$143.10	$143.10
Purchase #6	$20.30	4.177%	$21.1479	$21.15	$21.15	$21.10
Purchase #7	$72.33	3.670%	$74.9845	$74.98	$75.00	$75.00
7 purchase totals =	$947.57		$1,016.2469	$1,016.24	$1,016.25	$1,016.20