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	$165.84	6.625%	$176.8269	$176.83	$176.85	$176.80
Purchase #2	$203.83	13.351%	$231.0433	$231.04	$231.05	$231.00
Purchase #3	$78.87	4.612%	$82.5075	$82.51	$82.50	$82.50
Purchase #4	$149.88	10.762%	$166.0101	$166.01	$166.00	$166.00
Purchase #5	$69.29	9.528%	$75.892	$75.89	$75.90	$75.90
Purchase #6	$230.77	10.659%	$255.3678	$255.37	$255.35	$255.40
Purchase #7	$54.64	11.486%	$60.916	$60.92	$60.90	$60.90
7 purchase totals =	$953.12		$1,048.5636	$1,048.57	$1,048.55	$1,048.50