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	$216.94	3.528%	$224.5936	$224.59	$224.60	$224.60
Purchase #2	$94.31	12.218%	$105.8328	$105.83	$105.85	$105.80
Purchase #3	$89.94	12.845%	$101.4928	$101.49	$101.50	$101.50
Purchase #4	$157.38	6.250%	$167.2163	$167.22	$167.20	$167.20
Purchase #5	$170.74	5.449%	$180.0436	$180.04	$180.05	$180.00
Purchase #6	$38.65	9.782%	$42.4307	$42.43	$42.45	$42.40
Purchase #7	$232.51	3.516%	$240.6851	$240.69	$240.70	$240.70
7 purchase totals =	$1,000.47		$1,062.2949	$1,062.29	$1,062.35	$1,062.20