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	$33.64	10.613%	$37.2102	$37.21	$37.20	$37.20
Purchase #2	$223.92	6.597%	$238.692	$238.69	$238.70	$238.70
Purchase #3	$244.55	11.438%	$272.5216	$272.52	$272.50	$272.50
Purchase #4	$97.35	11.218%	$108.2707	$108.27	$108.25	$108.30
Purchase #5	$238.46	7.305%	$255.8795	$255.88	$255.90	$255.90
Purchase #6	$61.94	6.322%	$65.8558	$65.86	$65.85	$65.90
Purchase #7	$68.88	10.293%	$75.9698	$75.97	$75.95	$76.00
7 purchase totals =	$968.74		$1,054.3996	$1,054.40	$1,054.35	$1,054.50