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	$206.28	7.808%	$222.3863	$222.39	$222.40	$222.40
Purchase #2	$72.78	13.125%	$82.3324	$82.33	$82.35	$82.30
Purchase #3	$18.78	12.134%	$21.0588	$21.06	$21.05	$21.10
Purchase #4	$176.79	8.659%	$192.0982	$192.10	$192.10	$192.10
Purchase #5	$218.26	8.158%	$236.0657	$236.07	$236.05	$236.10
Purchase #6	$192.59	9.822%	$211.5062	$211.51	$211.50	$211.50
Purchase #7	$111.83	11.616%	$124.8202	$124.82	$124.80	$124.80
7 purchase totals =	$997.31		$1,090.2678	$1,090.28	$1,090.25	$1,090.30