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	$200.30	9.869%	$220.0676	$220.07	$220.05	$220.10
Purchase #2	$218.41	10.510%	$241.3649	$241.36	$241.35	$241.40
Purchase #3	$70.50	13.643%	$80.1183	$80.12	$80.10	$80.10
Purchase #4	$157.42	12.133%	$176.5198	$176.52	$176.50	$176.50
Purchase #5	$33.83	3.686%	$35.077	$35.08	$35.10	$35.10
Purchase #6	$130.47	8.449%	$141.4934	$141.49	$141.50	$141.50
Purchase #7	$189.88	5.642%	$200.593	$200.59	$200.60	$200.60
7 purchase totals =	$1,000.81		$1,095.2340	$1,095.23	$1,095.20	$1,095.30