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	$212.79	4.355%	$222.057	$222.06	$222.05	$222.10
Purchase #2	$245.49	5.666%	$259.3995	$259.40	$259.40	$259.40
Purchase #3	$247.29	3.268%	$255.3714	$255.37	$255.35	$255.40
Purchase #4	$145.46	13.225%	$164.6971	$164.70	$164.70	$164.70
Purchase #5	$59.37	10.175%	$65.4109	$65.41	$65.40	$65.40
Purchase #6	$50.75	3.817%	$52.6871	$52.69	$52.70	$52.70
Purchase #7	$231.33	7.388%	$248.4207	$248.42	$248.40	$248.40
7 purchase totals =	$1,192.48		$1,268.0437	$1,268.05	$1,268.00	$1,268.10