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	$42.56	8.526%	$46.1887	$46.19	$46.20	$46.20
Purchase #2	$113.38	12.177%	$127.1863	$127.19	$127.20	$127.20
Purchase #3	$185.35	8.158%	$200.4709	$200.47	$200.45	$200.50
Purchase #4	$100.56	8.284%	$108.8904	$108.89	$108.90	$108.90
Purchase #5	$214.91	11.174%	$238.924	$238.92	$238.90	$238.90
Purchase #6	$136.58	8.710%	$148.4761	$148.48	$148.50	$148.50
Purchase #7	$155.30	4.717%	$162.6255	$162.63	$162.65	$162.60
7 purchase totals =	$948.64		$1,032.7619	$1,032.77	$1,032.80	$1,032.80