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	$72.40	5.736%	$76.5529	$76.55	$76.55	$76.60
Purchase #2	$160.35	7.347%	$172.1309	$172.13	$172.15	$172.10
Purchase #3	$242.59	4.204%	$252.7885	$252.79	$252.80	$252.80
Purchase #4	$229.79	5.469%	$242.3572	$242.36	$242.35	$242.40
Purchase #5	$110.67	3.697%	$114.7615	$114.76	$114.75	$114.80
Purchase #6	$66.61	8.786%	$72.4624	$72.46	$72.45	$72.50
Purchase #7	$105.84	12.312%	$118.871	$118.87	$118.85	$118.90
7 purchase totals =	$988.25		$1,049.9244	$1,049.92	$1,049.90	$1,050.10