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	$107.34	11.239%	$119.4039	$119.40	$119.40	$119.40
Purchase #2	$123.43	3.826%	$128.1524	$128.15	$128.15	$128.20
Purchase #3	$177.89	11.372%	$198.1197	$198.12	$198.10	$198.10
Purchase #4	$145.81	7.851%	$157.2575	$157.26	$157.25	$157.30
Purchase #5	$228.52	9.638%	$250.5448	$250.54	$250.55	$250.50
Purchase #6	$184.42	6.300%	$196.0385	$196.04	$196.05	$196.00
Purchase #7	$112.56	4.696%	$117.8458	$117.85	$117.85	$117.80
7 purchase totals =	$1,079.97		$1,167.3626	$1,167.36	$1,167.35	$1,167.30