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	$65.95	8.714%	$71.6969	$71.70	$71.70	$71.70
Purchase #2	$131.43	10.412%	$145.1145	$145.11	$145.10	$145.10
Purchase #3	$74.89	4.205%	$78.0391	$78.04	$78.05	$78.00
Purchase #4	$44.27	7.523%	$47.6004	$47.60	$47.60	$47.60
Purchase #5	$140.52	4.250%	$146.4921	$146.49	$146.50	$146.50
Purchase #6	$35.93	8.279%	$38.9046	$38.90	$38.90	$38.90
Purchase #7	$199.38	8.596%	$216.5187	$216.52	$216.50	$216.50
7 purchase totals =	$692.37		$744.3663	$744.36	$744.35	$744.30