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	$205.42	3.280%	$212.1578	$212.16	$212.15	$212.20
Purchase #2	$177.53	10.659%	$196.4529	$196.45	$196.45	$196.50
Purchase #3	$140.78	12.109%	$157.8271	$157.83	$157.85	$157.80
Purchase #4	$24.80	11.516%	$27.656	$27.66	$27.65	$27.70
Purchase #5	$189.67	11.696%	$211.8538	$211.85	$211.85	$211.90
Purchase #6	$247.47	4.170%	$257.7895	$257.79	$257.80	$257.80
Purchase #7	$101.55	9.330%	$111.0246	$111.02	$111.00	$111.00
7 purchase totals =	$1,087.22		$1,174.7617	$1,174.76	$1,174.75	$1,174.90