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	$208.36	5.416%	$219.6448	$219.64	$219.65	$219.60
Purchase #2	$54.71	12.689%	$61.6522	$61.65	$61.65	$61.70
Purchase #3	$162.35	5.666%	$171.5488	$171.55	$171.55	$171.50
Purchase #4	$156.72	10.699%	$173.4875	$173.49	$173.50	$173.50
Purchase #5	$245.84	4.344%	$256.5193	$256.52	$256.50	$256.50
Purchase #6	$126.69	11.510%	$141.272	$141.27	$141.25	$141.30
Purchase #7	$166.44	6.253%	$176.8475	$176.85	$176.85	$176.80
7 purchase totals =	$1,121.11		$1,200.9721	$1,200.97	$1,200.95	$1,200.90