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	$225.94	6.553%	$240.7458	$240.75	$240.75	$240.70
Purchase #2	$91.29	13.836%	$103.9209	$103.92	$103.90	$103.90
Purchase #3	$128.46	9.209%	$140.2899	$140.29	$140.30	$140.30
Purchase #4	$119.68	7.483%	$128.6357	$128.64	$128.65	$128.60
Purchase #5	$61.87	5.440%	$65.2357	$65.24	$65.25	$65.20
Purchase #6	$228.25	7.588%	$245.5696	$245.57	$245.55	$245.60
Purchase #7	$176.94	5.592%	$186.8345	$186.83	$186.85	$186.80
7 purchase totals =	$1,032.43		$1,111.2321	$1,111.24	$1,111.25	$1,111.10