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	$126.92	3.372%	$131.1997	$131.20	$131.20	$131.20
Purchase #2	$10.90	12.420%	$12.2538	$12.25	$12.25	$12.30
Purchase #3	$138.60	4.188%	$144.4046	$144.40	$144.40	$144.40
Purchase #4	$174.52	12.829%	$196.9092	$196.91	$196.90	$196.90
Purchase #5	$235.37	10.274%	$259.5519	$259.55	$259.55	$259.60
Purchase #6	$154.42	10.574%	$170.7484	$170.75	$170.75	$170.70
Purchase #7	$14.70	12.119%	$16.4815	$16.48	$16.50	$16.50
7 purchase totals =	$855.43		$931.5491	$931.54	$931.55	$931.60