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	$214.57	12.514%	$241.4213	$241.42	$241.40	$241.40
Purchase #2	$46.48	11.256%	$51.7118	$51.71	$51.70	$51.70
Purchase #3	$124.37	5.387%	$131.0698	$131.07	$131.05	$131.10
Purchase #4	$45.28	3.833%	$47.0156	$47.02	$47.00	$47.00
Purchase #5	$162.53	11.248%	$180.8114	$180.81	$180.80	$180.80
Purchase #6	$85.87	5.614%	$90.6907	$90.69	$90.70	$90.70
Purchase #7	$167.42	8.584%	$181.7913	$181.79	$181.80	$181.80
7 purchase totals =	$846.52		$924.5119	$924.51	$924.45	$924.50