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	$198.91	8.598%	$216.0123	$216.01	$216.00	$216.00
Purchase #2	$156.76	6.760%	$167.357	$167.36	$167.35	$167.40
Purchase #3	$19.69	9.495%	$21.5596	$21.56	$21.55	$21.60
Purchase #4	$36.52	11.244%	$40.6263	$40.63	$40.65	$40.60
Purchase #5	$41.61	13.724%	$47.3206	$47.32	$47.30	$47.30
Purchase #6	$120.94	11.751%	$135.1517	$135.15	$135.15	$135.20
Purchase #7	$53.86	10.620%	$59.5799	$59.58	$59.60	$59.60
7 purchase totals =	$628.29		$687.6074	$687.61	$687.60	$687.70