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	$202.89	10.381%	$223.952	$223.95	$223.95	$224.00
Purchase #2	$78.52	5.675%	$82.976	$82.98	$83.00	$83.00
Purchase #3	$41.92	8.713%	$45.5725	$45.57	$45.55	$45.60
Purchase #4	$43.64	10.672%	$48.2973	$48.30	$48.30	$48.30
Purchase #5	$30.43	9.502%	$33.3215	$33.32	$33.30	$33.30
Purchase #6	$68.91	3.694%	$71.4555	$71.46	$71.45	$71.50
Purchase #7	$106.94	4.799%	$112.0721	$112.07	$112.05	$112.10
7 purchase totals =	$573.25		$617.6469	$617.65	$617.60	$617.80