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	$195.93	9.841%	$215.2115	$215.21	$215.20	$215.20
Purchase #2	$141.78	3.560%	$146.8274	$146.83	$146.85	$146.80
Purchase #3	$41.32	4.357%	$43.1203	$43.12	$43.10	$43.10
Purchase #4	$59.51	10.649%	$65.8472	$65.85	$65.85	$65.80
Purchase #5	$10.25	4.851%	$10.7472	$10.75	$10.75	$10.70
Purchase #6	$7.82	11.183%	$8.6945	$8.69	$8.70	$8.70
Purchase #7	$62.73	7.793%	$67.6185	$67.62	$67.60	$67.60
7 purchase totals =	$519.34		$558.0666	$558.07	$558.05	$557.90