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	$115.61	10.688%	$127.9664	$127.97	$127.95	$128.00
Purchase #2	$169.59	7.244%	$181.8751	$181.88	$181.90	$181.90
Purchase #3	$18.74	9.730%	$20.5634	$20.56	$20.55	$20.60
Purchase #4	$93.80	8.232%	$101.5216	$101.52	$101.50	$101.50
Purchase #5	$59.73	5.351%	$62.9262	$62.93	$62.95	$62.90
Purchase #6	$170.50	13.617%	$193.717	$193.72	$193.70	$193.70
Purchase #7	$48.92	10.665%	$54.1373	$54.14	$54.15	$54.10
7 purchase totals =	$676.89		$742.7070	$742.72	$742.70	$742.70