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	$179.74	10.636%	$198.8571	$198.86	$198.85	$198.90
Purchase #2	$149.86	11.804%	$167.5495	$167.55	$167.55	$167.50
Purchase #3	$105.71	3.688%	$109.6086	$109.61	$109.60	$109.60
Purchase #4	$96.83	11.306%	$107.7776	$107.78	$107.80	$107.80
Purchase #5	$234.25	8.737%	$254.7164	$254.72	$254.70	$254.70
Purchase #6	$11.86	13.514%	$13.4628	$13.46	$13.45	$13.50
Purchase #7	$157.57	5.637%	$166.4522	$166.45	$166.45	$166.50
7 purchase totals =	$935.82		$1,018.4242	$1,018.43	$1,018.40	$1,018.50