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	$167.83	7.722%	$180.7898	$180.79	$180.80	$180.80
Purchase #2	$139.32	8.537%	$151.2137	$151.21	$151.20	$151.20
Purchase #3	$142.76	6.690%	$152.3106	$152.31	$152.30	$152.30
Purchase #4	$52.88	4.186%	$55.0936	$55.09	$55.10	$55.10
Purchase #5	$148.31	5.493%	$156.4567	$156.46	$156.45	$156.50
Purchase #6	$215.36	9.131%	$235.0245	$235.02	$235.00	$235.00
Purchase #7	$144.89	5.315%	$152.5909	$152.59	$152.60	$152.60
7 purchase totals =	$1,011.35		$1,083.4798	$1,083.47	$1,083.45	$1,083.50