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	$99.39	9.549%	$108.8808	$108.88	$108.90	$108.90
Purchase #2	$123.53	5.412%	$130.2154	$130.22	$130.20	$130.20
Purchase #3	$17.83	3.135%	$18.389	$18.39	$18.40	$18.40
Purchase #4	$176.67	11.292%	$196.6196	$196.62	$196.60	$196.60
Purchase #5	$227.44	11.231%	$252.9838	$252.98	$253.00	$253.00
Purchase #6	$82.35	8.527%	$89.372	$89.37	$89.35	$89.40
Purchase #7	$237.97	6.368%	$253.1239	$253.12	$253.10	$253.10
7 purchase totals =	$965.18		$1,049.5845	$1,049.58	$1,049.55	$1,049.60