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	$232.92	7.141%	$249.5528	$249.55	$249.55	$249.60
Purchase #2	$18.75	8.782%	$20.3966	$20.40	$20.40	$20.40
Purchase #3	$109.61	7.322%	$117.6356	$117.64	$117.65	$117.60
Purchase #4	$56.32	5.813%	$59.5939	$59.59	$59.60	$59.60
Purchase #5	$220.88	3.112%	$227.7538	$227.75	$227.75	$227.80
Purchase #6	$151.90	3.576%	$157.3319	$157.33	$157.35	$157.30
Purchase #7	$179.32	10.556%	$198.249	$198.25	$198.25	$198.20
7 purchase totals =	$969.70		$1,030.5136	$1,030.51	$1,030.55	$1,030.50