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	$175.30	5.393%	$184.7539	$184.75	$184.75	$184.80
Purchase #2	$35.88	3.162%	$37.0145	$37.01	$37.00	$37.00
Purchase #3	$240.29	9.773%	$263.7735	$263.77	$263.75	$263.80
Purchase #4	$192.28	8.849%	$209.2949	$209.29	$209.30	$209.30
Purchase #5	$241.62	5.728%	$255.46	$255.46	$255.45	$255.50
Purchase #6	$40.56	6.278%	$43.1064	$43.11	$43.10	$43.10
Purchase #7	$12.42	3.511%	$12.8561	$12.86	$12.85	$12.90
7 purchase totals =	$938.35		$1,006.2593	$1,006.25	$1,006.20	$1,006.40