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	$68.89	4.415%	$71.9315	$71.93	$71.95	$71.90
Purchase #2	$117.53	12.382%	$132.0826	$132.08	$132.10	$132.10
Purchase #3	$120.69	5.464%	$127.2845	$127.28	$127.30	$127.30
Purchase #4	$233.70	3.451%	$241.765	$241.77	$241.75	$241.80
Purchase #5	$96.31	8.637%	$104.6283	$104.63	$104.65	$104.60
Purchase #6	$40.79	7.119%	$43.6938	$43.69	$43.70	$43.70
Purchase #7	$206.45	11.142%	$229.4527	$229.45	$229.45	$229.50
7 purchase totals =	$884.36		$950.8384	$950.83	$950.90	$950.90