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	$55.64	12.554%	$62.625	$62.63	$62.65	$62.60
Purchase #2	$150.33	12.622%	$169.3047	$169.30	$169.30	$169.30
Purchase #3	$246.27	10.383%	$271.8402	$271.84	$271.85	$271.80
Purchase #4	$142.42	10.395%	$157.2246	$157.22	$157.20	$157.20
Purchase #5	$83.60	6.680%	$89.1845	$89.18	$89.20	$89.20
Purchase #6	$198.25	4.298%	$206.7708	$206.77	$206.75	$206.80
Purchase #7	$42.81	11.738%	$47.835	$47.84	$47.85	$47.80
7 purchase totals =	$919.32		$1,004.7848	$1,004.78	$1,004.80	$1,004.70