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	$173.27	13.244%	$196.2179	$196.22	$196.20	$196.20
Purchase #2	$174.30	7.545%	$187.4509	$187.45	$187.45	$187.50
Purchase #3	$29.88	4.351%	$31.1801	$31.18	$31.20	$31.20
Purchase #4	$38.98	9.135%	$42.5408	$42.54	$42.55	$42.50
Purchase #5	$197.54	11.183%	$219.6309	$219.63	$219.65	$219.60
Purchase #6	$23.43	8.473%	$25.4152	$25.42	$25.40	$25.40
Purchase #7	$199.77	8.854%	$217.4576	$217.46	$217.45	$217.50
7 purchase totals =	$837.17		$919.8934	$919.90	$919.90	$919.90