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	$243.87	10.350%	$269.1105	$269.11	$269.10	$269.10
Purchase #2	$43.90	3.658%	$45.5059	$45.51	$45.50	$45.50
Purchase #3	$212.45	4.491%	$221.9911	$221.99	$222.00	$222.00
Purchase #4	$128.51	12.454%	$144.5146	$144.51	$144.50	$144.50
Purchase #5	$183.81	8.381%	$199.2151	$199.22	$199.20	$199.20
Purchase #6	$81.50	12.334%	$91.5522	$91.55	$91.55	$91.60
Purchase #7	$132.59	8.217%	$143.4849	$143.48	$143.50	$143.50
7 purchase totals =	$1,026.63		$1,115.3743	$1,115.37	$1,115.35	$1,115.40