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	$231.32	7.541%	$248.7638	$248.76	$248.75	$248.80
Purchase #2	$82.44	3.544%	$85.3617	$85.36	$85.35	$85.40
Purchase #3	$99.37	5.127%	$104.4647	$104.46	$104.45	$104.50
Purchase #4	$19.39	5.152%	$20.389	$20.39	$20.40	$20.40
Purchase #5	$214.94	6.405%	$228.7069	$228.71	$228.70	$228.70
Purchase #6	$56.47	7.681%	$60.8075	$60.81	$60.80	$60.80
Purchase #7	$161.57	6.769%	$172.5067	$172.51	$172.50	$172.50
7 purchase totals =	$865.50		$921.0003	$921.00	$920.95	$921.10