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	$36.49	4.244%	$38.0386	$38.04	$38.05	$38.00
Purchase #2	$37.81	13.435%	$42.8898	$42.89	$42.90	$42.90
Purchase #3	$82.68	12.582%	$93.0828	$93.08	$93.10	$93.10
Purchase #4	$10.43	12.396%	$11.7229	$11.72	$11.70	$11.70
Purchase #5	$93.32	12.386%	$104.8786	$104.88	$104.90	$104.90
Purchase #6	$99.46	4.651%	$104.0859	$104.09	$104.10	$104.10
Purchase #7	$121.54	8.364%	$131.7056	$131.71	$131.70	$131.70
7 purchase totals =	$481.73		$526.4042	$526.41	$526.45	$526.40