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	$151.36	8.396%	$164.0682	$164.07	$164.05	$164.10
Purchase #2	$123.40	13.707%	$140.3144	$140.31	$140.30	$140.30
Purchase #3	$38.42	4.131%	$40.0071	$40.01	$40.00	$40.00
Purchase #4	$182.91	8.719%	$198.8579	$198.86	$198.85	$198.90
Purchase #5	$151.60	5.754%	$160.3231	$160.32	$160.30	$160.30
Purchase #6	$147.32	5.774%	$155.8263	$155.83	$155.85	$155.80
Purchase #7	$240.52	6.755%	$256.7671	$256.77	$256.75	$256.80
7 purchase totals =	$1,035.53		$1,116.1641	$1,116.17	$1,116.10	$1,116.20