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	$150.64	9.458%	$164.8875	$164.89	$164.90	$164.90
Purchase #2	$88.62	11.565%	$98.8689	$98.87	$98.85	$98.90
Purchase #3	$18.74	5.239%	$19.7218	$19.72	$19.70	$19.70
Purchase #4	$83.69	3.485%	$86.6066	$86.61	$86.60	$86.60
Purchase #5	$99.40	8.116%	$107.4673	$107.47	$107.45	$107.50
Purchase #6	$6.28	9.112%	$6.8522	$6.85	$6.85	$6.90
Purchase #7	$151.94	11.553%	$169.4936	$169.49	$169.50	$169.50
7 purchase totals =	$599.31		$653.8979	$653.90	$653.85	$654.00