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	$96.34	7.401%	$103.4701	$103.47	$103.45	$103.50
Purchase #2	$68.77	12.465%	$77.3422	$77.34	$77.35	$77.30
Purchase #3	$8.67	9.481%	$9.492	$9.49	$9.50	$9.50
Purchase #4	$53.96	10.413%	$59.5789	$59.58	$59.60	$59.60
Purchase #5	$160.37	8.510%	$174.0175	$174.02	$174.00	$174.00
Purchase #6	$114.75	4.472%	$119.8816	$119.88	$119.90	$119.90
Purchase #7	$205.83	11.607%	$229.7207	$229.72	$229.70	$229.70
7 purchase totals =	$708.69		$773.5030	$773.50	$773.50	$773.50