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	$124.36	13.839%	$141.5702	$141.57	$141.55	$141.60
Purchase #2	$19.45	7.297%	$20.8693	$20.87	$20.85	$20.90
Purchase #3	$47.85	3.870%	$49.7018	$49.70	$49.70	$49.70
Purchase #4	$157.45	10.870%	$174.5648	$174.56	$174.55	$174.60
Purchase #5	$91.45	3.218%	$94.3929	$94.39	$94.40	$94.40
Purchase #6	$34.59	9.563%	$37.8978	$37.90	$37.90	$37.90
Purchase #7	$117.88	11.729%	$131.7061	$131.71	$131.70	$131.70
7 purchase totals =	$593.03		$650.7029	$650.70	$650.65	$650.80