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	$43.67	4.409%	$45.5954	$45.60	$45.60	$45.60
Purchase #2	$169.46	13.476%	$192.2964	$192.30	$192.30	$192.30
Purchase #3	$82.58	11.146%	$91.7844	$91.78	$91.80	$91.80
Purchase #4	$150.67	4.306%	$157.1579	$157.16	$157.15	$157.20
Purchase #5	$216.58	6.154%	$229.9083	$229.91	$229.90	$229.90
Purchase #6	$170.63	6.605%	$181.9001	$181.90	$181.90	$181.90
Purchase #7	$207.91	10.116%	$228.9422	$228.94	$228.95	$228.90
7 purchase totals =	$1,041.50		$1,127.5847	$1,127.59	$1,127.60	$1,127.60