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	$113.43	12.319%	$127.4034	$127.40	$127.40	$127.40
Purchase #2	$246.46	13.663%	$280.1338	$280.13	$280.15	$280.10
Purchase #3	$157.79	6.659%	$168.2972	$168.30	$168.30	$168.30
Purchase #4	$155.38	10.389%	$171.5224	$171.52	$171.50	$171.50
Purchase #5	$185.42	13.493%	$210.4387	$210.44	$210.45	$210.40
Purchase #6	$49.58	10.289%	$54.6813	$54.68	$54.70	$54.70
Purchase #7	$24.66	10.168%	$27.1674	$27.17	$27.15	$27.20
7 purchase totals =	$932.72		$1,039.6442	$1,039.64	$1,039.65	$1,039.60