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	$137.38	9.161%	$149.9654	$149.97	$149.95	$150.00
Purchase #2	$144.71	8.409%	$156.8787	$156.88	$156.90	$156.90
Purchase #3	$173.32	12.850%	$195.5916	$195.59	$195.60	$195.60
Purchase #4	$66.34	8.410%	$71.9192	$71.92	$71.90	$71.90
Purchase #5	$20.25	5.717%	$21.4077	$21.41	$21.40	$21.40
Purchase #6	$231.74	12.580%	$260.8929	$260.89	$260.90	$260.90
Purchase #7	$212.50	4.617%	$222.3111	$222.31	$222.30	$222.30
7 purchase totals =	$986.24		$1,078.9666	$1,078.97	$1,078.95	$1,079.00