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	$183.29	3.555%	$189.806	$189.81	$189.80	$189.80
Purchase #2	$55.89	3.433%	$57.8087	$57.81	$57.80	$57.80
Purchase #3	$11.40	13.730%	$12.9652	$12.97	$12.95	$13.00
Purchase #4	$64.37	11.299%	$71.6432	$71.64	$71.65	$71.60
Purchase #5	$40.82	5.207%	$42.9455	$42.95	$42.95	$42.90
Purchase #6	$189.74	4.379%	$198.0487	$198.05	$198.05	$198.00
Purchase #7	$153.34	10.139%	$168.8871	$168.89	$168.90	$168.90
7 purchase totals =	$698.85		$742.1044	$742.12	$742.10	$742.00