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	$117.95	3.693%	$122.3059	$122.31	$122.30	$122.30
Purchase #2	$102.52	11.689%	$114.5036	$114.50	$114.50	$114.50
Purchase #3	$141.27	12.488%	$158.9118	$158.91	$158.90	$158.90
Purchase #4	$50.96	8.705%	$55.3961	$55.40	$55.40	$55.40
Purchase #5	$78.28	4.748%	$81.9967	$82.00	$82.00	$82.00
Purchase #6	$74.31	3.422%	$76.8529	$76.85	$76.85	$76.90
Purchase #7	$163.67	6.501%	$174.3102	$174.31	$174.30	$174.30
7 purchase totals =	$728.96		$784.2772	$784.28	$784.25	$784.30