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	$101.31	5.754%	$107.1394	$107.14	$107.15	$107.10
Purchase #2	$164.67	11.107%	$182.9599	$182.96	$182.95	$183.00
Purchase #3	$53.51	7.462%	$57.5029	$57.50	$57.50	$57.50
Purchase #4	$152.33	4.327%	$158.9213	$158.92	$158.90	$158.90
Purchase #5	$136.72	11.623%	$152.611	$152.61	$152.60	$152.60
Purchase #6	$72.83	12.847%	$82.1865	$82.19	$82.20	$82.20
Purchase #7	$37.47	11.474%	$41.7693	$41.77	$41.75	$41.80
7 purchase totals =	$718.84		$783.0903	$783.09	$783.05	$783.10