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	$244.84	10.222%	$269.8675	$269.87	$269.85	$269.90
Purchase #2	$204.41	8.300%	$221.376	$221.38	$221.40	$221.40
Purchase #3	$53.83	3.807%	$55.8793	$55.88	$55.90	$55.90
Purchase #4	$183.70	4.684%	$192.3045	$192.30	$192.30	$192.30
Purchase #5	$118.71	12.211%	$133.2057	$133.21	$133.20	$133.20
Purchase #6	$75.86	8.448%	$82.2687	$82.27	$82.25	$82.30
Purchase #7	$94.58	11.662%	$105.6099	$105.61	$105.60	$105.60
7 purchase totals =	$975.93		$1,060.5116	$1,060.52	$1,060.50	$1,060.60