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	$51.43	6.522%	$54.7843	$54.78	$54.80	$54.80
Purchase #2	$150.45	11.125%	$167.1876	$167.19	$167.20	$167.20
Purchase #3	$206.85	6.794%	$220.9034	$220.90	$220.90	$220.90
Purchase #4	$124.30	12.873%	$140.3011	$140.30	$140.30	$140.30
Purchase #5	$29.36	11.255%	$32.6645	$32.66	$32.65	$32.70
Purchase #6	$230.52	11.454%	$256.9238	$256.92	$256.90	$256.90
Purchase #7	$160.78	3.434%	$166.3012	$166.30	$166.30	$166.30
7 purchase totals =	$953.69		$1,039.0659	$1,039.05	$1,039.05	$1,039.10