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	$86.89	8.340%	$94.1366	$94.14	$94.15	$94.10
Purchase #2	$148.63	4.567%	$155.4179	$155.42	$155.40	$155.40
Purchase #3	$144.67	5.187%	$152.174	$152.17	$152.15	$152.20
Purchase #4	$114.36	3.172%	$117.9875	$117.99	$118.00	$118.00
Purchase #5	$178.87	3.659%	$185.4149	$185.41	$185.40	$185.40
Purchase #6	$93.92	10.397%	$103.6849	$103.68	$103.70	$103.70
Purchase #7	$244.78	11.564%	$273.0864	$273.09	$273.10	$273.10
7 purchase totals =	$1,012.12		$1,081.9022	$1,081.90	$1,081.90	$1,081.90