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	$194.37	7.298%	$208.5551	$208.56	$208.55	$208.60
Purchase #2	$173.37	13.592%	$196.9345	$196.93	$196.95	$196.90
Purchase #3	$246.98	13.764%	$280.9743	$280.97	$280.95	$281.00
Purchase #4	$147.46	5.808%	$156.0245	$156.02	$156.00	$156.00
Purchase #5	$146.94	5.684%	$155.2921	$155.29	$155.30	$155.30
Purchase #6	$202.86	4.750%	$212.4959	$212.50	$212.50	$212.50
Purchase #7	$117.80	4.648%	$123.2753	$123.28	$123.30	$123.30
7 purchase totals =	$1,229.78		$1,333.5517	$1,333.55	$1,333.55	$1,333.60