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	$69.57	9.815%	$76.3983	$76.40	$76.40	$76.40
Purchase #2	$135.71	11.435%	$151.2284	$151.23	$151.25	$151.20
Purchase #3	$164.48	5.605%	$173.6991	$173.70	$173.70	$173.70
Purchase #4	$86.87	10.216%	$95.7446	$95.74	$95.75	$95.70
Purchase #5	$154.44	7.264%	$165.6585	$165.66	$165.65	$165.70
Purchase #6	$121.58	5.145%	$127.8353	$127.84	$127.85	$127.80
Purchase #7	$127.78	4.773%	$133.8789	$133.88	$133.90	$133.90
7 purchase totals =	$860.43		$924.4431	$924.45	$924.50	$924.40