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	$163.36	6.798%	$174.4652	$174.47	$174.45	$174.50
Purchase #2	$145.51	13.214%	$164.7377	$164.74	$164.75	$164.70
Purchase #3	$164.71	11.256%	$183.2498	$183.25	$183.25	$183.20
Purchase #4	$164.70	5.333%	$173.4835	$173.48	$173.50	$173.50
Purchase #5	$46.78	4.829%	$49.039	$49.04	$49.05	$49.00
Purchase #6	$94.57	5.865%	$100.1165	$100.12	$100.10	$100.10
Purchase #7	$44.71	12.792%	$50.4293	$50.43	$50.45	$50.40
7 purchase totals =	$824.34		$895.5210	$895.53	$895.55	$895.40