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	$180.94	6.432%	$192.5781	$192.58	$192.60	$192.60
Purchase #2	$66.92	7.796%	$72.1371	$72.14	$72.15	$72.10
Purchase #3	$90.54	11.165%	$100.6488	$100.65	$100.65	$100.60
Purchase #4	$85.47	3.787%	$88.7067	$88.71	$88.70	$88.70
Purchase #5	$78.49	8.685%	$85.3069	$85.31	$85.30	$85.30
Purchase #6	$228.71	5.433%	$241.1358	$241.14	$241.15	$241.10
Purchase #7	$160.81	3.257%	$166.0476	$166.05	$166.05	$166.00
7 purchase totals =	$891.88		$946.5610	$946.58	$946.60	$946.40