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	$233.85	10.682%	$258.8299	$258.83	$258.85	$258.80
Purchase #2	$131.47	10.592%	$145.3953	$145.40	$145.40	$145.40
Purchase #3	$135.51	11.496%	$151.0882	$151.09	$151.10	$151.10
Purchase #4	$130.52	11.768%	$145.8796	$145.88	$145.90	$145.90
Purchase #5	$16.44	13.589%	$18.674	$18.67	$18.65	$18.70
Purchase #6	$91.94	13.685%	$104.522	$104.52	$104.50	$104.50
Purchase #7	$244.94	7.582%	$263.5114	$263.51	$263.50	$263.50
7 purchase totals =	$984.67		$1,087.9004	$1,087.90	$1,087.90	$1,087.90