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	$118.90	5.211%	$125.0959	$125.10	$125.10	$125.10
Purchase #2	$60.59	3.234%	$62.5495	$62.55	$62.55	$62.50
Purchase #3	$52.33	4.616%	$54.7456	$54.75	$54.75	$54.70
Purchase #4	$45.68	9.360%	$49.9556	$49.96	$49.95	$50.00
Purchase #5	$244.60	10.181%	$269.5027	$269.50	$269.50	$269.50
Purchase #6	$93.52	7.548%	$100.5789	$100.58	$100.60	$100.60
Purchase #7	$115.30	10.230%	$127.0952	$127.10	$127.10	$127.10
7 purchase totals =	$730.92		$789.5234	$789.54	$789.55	$789.50