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	$202.77	10.297%	$223.6492	$223.65	$223.65	$223.60
Purchase #2	$54.53	8.733%	$59.2921	$59.29	$59.30	$59.30
Purchase #3	$45.97	13.671%	$52.2546	$52.25	$52.25	$52.30
Purchase #4	$228.38	3.544%	$236.4738	$236.47	$236.45	$236.50
Purchase #5	$36.67	5.191%	$38.5735	$38.57	$38.55	$38.60
Purchase #6	$40.86	10.604%	$45.1928	$45.19	$45.20	$45.20
Purchase #7	$43.85	4.290%	$45.7312	$45.73	$45.75	$45.70
7 purchase totals =	$653.03		$701.1672	$701.15	$701.15	$701.20