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	$32.65	8.332%	$35.3704	$35.37	$35.35	$35.40
Purchase #2	$69.97	11.546%	$78.0487	$78.05	$78.05	$78.00
Purchase #3	$138.92	12.465%	$156.2364	$156.24	$156.25	$156.20
Purchase #4	$43.37	8.132%	$46.8968	$46.90	$46.90	$46.90
Purchase #5	$96.67	3.304%	$99.864	$99.86	$99.85	$99.90
Purchase #6	$13.51	4.631%	$14.1356	$14.14	$14.15	$14.10
Purchase #7	$47.28	11.758%	$52.8392	$52.84	$52.85	$52.80
7 purchase totals =	$442.37		$483.3911	$483.40	$483.40	$483.30