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	$110.56	5.653%	$116.81	$116.81	$116.80	$116.80
Purchase #2	$104.78	8.809%	$114.0101	$114.01	$114.00	$114.00
Purchase #3	$79.36	11.212%	$88.2578	$88.26	$88.25	$88.30
Purchase #4	$164.52	10.388%	$181.6103	$181.61	$181.60	$181.60
Purchase #5	$192.53	10.312%	$212.3837	$212.38	$212.40	$212.40
Purchase #6	$250.71	9.536%	$274.6177	$274.62	$274.60	$274.60
Purchase #7	$190.69	9.481%	$208.7693	$208.77	$208.75	$208.80
7 purchase totals =	$1,093.15		$1,196.4589	$1,196.46	$1,196.40	$1,196.50