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	$219.83	5.498%	$231.9163	$231.92	$231.90	$231.90
Purchase #2	$110.98	9.286%	$121.2856	$121.29	$121.30	$121.30
Purchase #3	$46.49	13.640%	$52.8312	$52.83	$52.85	$52.80
Purchase #4	$112.41	13.765%	$127.8832	$127.88	$127.90	$127.90
Purchase #5	$40.32	6.504%	$42.9424	$42.94	$42.95	$42.90
Purchase #6	$55.57	10.789%	$61.5654	$61.57	$61.55	$61.60
Purchase #7	$175.86	4.443%	$183.6735	$183.67	$183.65	$183.70
7 purchase totals =	$761.46		$822.0976	$822.10	$822.10	$822.10