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	$55.82	11.749%	$62.3783	$62.38	$62.40	$62.40
Purchase #2	$12.86	3.113%	$13.2603	$13.26	$13.25	$13.30
Purchase #3	$160.71	4.302%	$167.6237	$167.62	$167.60	$167.60
Purchase #4	$104.51	12.370%	$117.4379	$117.44	$117.45	$117.40
Purchase #5	$209.96	11.523%	$234.1537	$234.15	$234.15	$234.20
Purchase #6	$187.37	4.647%	$196.0771	$196.08	$196.10	$196.10
Purchase #7	$37.41	9.669%	$41.0272	$41.03	$41.05	$41.00
7 purchase totals =	$768.64		$831.9582	$831.96	$832.00	$832.00