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	$101.88	9.734%	$111.797	$111.80	$111.80	$111.80
Purchase #2	$51.27	3.811%	$53.2239	$53.22	$53.20	$53.20
Purchase #3	$182.82	8.374%	$198.1293	$198.13	$198.15	$198.10
Purchase #4	$231.35	11.464%	$257.872	$257.87	$257.85	$257.90
Purchase #5	$212.60	4.141%	$221.4038	$221.40	$221.40	$221.40
Purchase #6	$44.73	13.723%	$50.8683	$50.87	$50.85	$50.90
Purchase #7	$182.74	13.133%	$206.7392	$206.74	$206.75	$206.70
7 purchase totals =	$1,007.39		$1,100.0335	$1,100.03	$1,100.00	$1,100.00