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	$54.52	13.454%	$61.8551	$61.86	$61.85	$61.90
Purchase #2	$174.97	9.681%	$191.9088	$191.91	$191.90	$191.90
Purchase #3	$104.37	3.718%	$108.2505	$108.25	$108.25	$108.30
Purchase #4	$219.54	5.296%	$231.1668	$231.17	$231.15	$231.20
Purchase #5	$58.68	5.186%	$61.7231	$61.72	$61.70	$61.70
Purchase #6	$45.87	12.131%	$51.4345	$51.43	$51.45	$51.40
Purchase #7	$217.35	4.604%	$227.3568	$227.36	$227.35	$227.40
7 purchase totals =	$875.30		$933.6956	$933.70	$933.65	$933.80