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	$100.44	3.472%	$103.9273	$103.93	$103.95	$103.90
Purchase #2	$171.82	10.734%	$190.2632	$190.26	$190.25	$190.30
Purchase #3	$165.46	12.175%	$185.6048	$185.60	$185.60	$185.60
Purchase #4	$82.73	6.840%	$88.3887	$88.39	$88.40	$88.40
Purchase #5	$6.67	4.291%	$6.9562	$6.96	$6.95	$7.00
Purchase #6	$12.80	13.464%	$14.5234	$14.52	$14.50	$14.50
Purchase #7	$128.44	10.415%	$141.817	$141.82	$141.80	$141.80
7 purchase totals =	$668.36		$731.4806	$731.48	$731.45	$731.50