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	$170.37	7.370%	$182.9263	$182.93	$182.95	$182.90
Purchase #2	$114.31	13.126%	$129.3143	$129.31	$129.30	$129.30
Purchase #3	$7.54	4.701%	$7.8945	$7.89	$7.90	$7.90
Purchase #4	$81.95	10.302%	$90.3925	$90.39	$90.40	$90.40
Purchase #5	$56.86	11.620%	$63.4671	$63.47	$63.45	$63.50
Purchase #6	$158.55	9.489%	$173.5948	$173.59	$173.60	$173.60
Purchase #7	$178.91	9.758%	$196.368	$196.37	$196.35	$196.40
7 purchase totals =	$768.49		$843.9575	$843.95	$843.95	$844.00