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	$195.82	4.249%	$204.1404	$204.14	$204.15	$204.10
Purchase #2	$82.97	8.867%	$90.3269	$90.33	$90.35	$90.30
Purchase #3	$14.30	4.178%	$14.8975	$14.90	$14.90	$14.90
Purchase #4	$169.40	8.830%	$184.358	$184.36	$184.35	$184.40
Purchase #5	$73.67	11.743%	$82.3211	$82.32	$82.30	$82.30
Purchase #6	$19.92	6.814%	$21.2773	$21.28	$21.30	$21.30
Purchase #7	$44.29	11.527%	$49.3953	$49.40	$49.40	$49.40
7 purchase totals =	$600.37		$646.7165	$646.73	$646.75	$646.70