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	$185.35	7.728%	$199.6738	$199.67	$199.65	$199.70
Purchase #2	$181.81	8.264%	$196.8348	$196.83	$196.85	$196.80
Purchase #3	$92.57	13.857%	$105.3974	$105.40	$105.40	$105.40
Purchase #4	$221.31	5.696%	$233.9158	$233.92	$233.90	$233.90
Purchase #5	$85.95	4.158%	$89.5238	$89.52	$89.50	$89.50
Purchase #6	$36.66	8.468%	$39.7644	$39.76	$39.75	$39.80
Purchase #7	$90.80	11.686%	$101.4109	$101.41	$101.40	$101.40
7 purchase totals =	$894.45		$966.5209	$966.51	$966.45	$966.50