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	$199.72	10.405%	$220.5009	$220.50	$220.50	$220.50
Purchase #2	$241.91	9.463%	$264.8019	$264.80	$264.80	$264.80
Purchase #3	$189.99	10.769%	$210.45	$210.45	$210.45	$210.50
Purchase #4	$205.93	8.521%	$223.4773	$223.48	$223.50	$223.50
Purchase #5	$95.86	9.581%	$105.0443	$105.04	$105.05	$105.00
Purchase #6	$21.90	5.152%	$23.0283	$23.03	$23.05	$23.00
Purchase #7	$34.93	8.621%	$37.9413	$37.94	$37.95	$37.90
7 purchase totals =	$990.24		$1,085.2440	$1,085.24	$1,085.30	$1,085.20