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	$130.45	8.649%	$141.7326	$141.73	$141.75	$141.70
Purchase #2	$47.82	3.646%	$49.5635	$49.56	$49.55	$49.60
Purchase #3	$114.66	13.847%	$130.537	$130.54	$130.55	$130.50
Purchase #4	$32.56	10.226%	$35.8896	$35.89	$35.90	$35.90
Purchase #5	$199.50	8.474%	$216.4056	$216.41	$216.40	$216.40
Purchase #6	$34.89	9.835%	$38.3214	$38.32	$38.30	$38.30
Purchase #7	$244.95	4.362%	$255.6347	$255.63	$255.65	$255.60
7 purchase totals =	$804.83		$868.0844	$868.08	$868.10	$868.00