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	$231.95	10.280%	$255.7945	$255.79	$255.80	$255.80
Purchase #2	$78.83	5.390%	$83.0789	$83.08	$83.10	$83.10
Purchase #3	$168.39	7.400%	$180.8509	$180.85	$180.85	$180.90
Purchase #4	$39.53	8.466%	$42.8766	$42.88	$42.90	$42.90
Purchase #5	$13.85	6.403%	$14.7368	$14.74	$14.75	$14.70
Purchase #6	$160.73	10.470%	$177.5584	$177.56	$177.55	$177.60
Purchase #7	$236.41	10.570%	$261.3985	$261.40	$261.40	$261.40
7 purchase totals =	$929.69		$1,016.2946	$1,016.30	$1,016.35	$1,016.40