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	$33.39	4.808%	$34.9954	$35.00	$35.00	$35.00
Purchase #2	$119.59	6.457%	$127.3119	$127.31	$127.30	$127.30
Purchase #3	$67.45	7.389%	$72.4339	$72.43	$72.45	$72.40
Purchase #4	$138.31	3.303%	$142.8784	$142.88	$142.90	$142.90
Purchase #5	$93.73	7.810%	$101.0503	$101.05	$101.05	$101.10
Purchase #6	$10.56	8.392%	$11.4462	$11.45	$11.45	$11.40
Purchase #7	$135.32	5.437%	$142.6773	$142.68	$142.70	$142.70
7 purchase totals =	$598.35		$632.7934	$632.80	$632.85	$632.80