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	$51.67	5.382%	$54.4509	$54.45	$54.45	$54.50
Purchase #2	$56.96	13.361%	$64.5704	$64.57	$64.55	$64.60
Purchase #3	$162.25	12.104%	$181.8887	$181.89	$181.90	$181.90
Purchase #4	$57.87	9.248%	$63.2218	$63.22	$63.20	$63.20
Purchase #5	$33.88	13.825%	$38.5639	$38.56	$38.55	$38.60
Purchase #6	$18.84	8.353%	$20.4137	$20.41	$20.40	$20.40
Purchase #7	$131.71	9.430%	$144.1303	$144.13	$144.15	$144.10
7 purchase totals =	$513.18		$567.2397	$567.23	$567.20	$567.30