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	$33.58	10.611%	$37.1432	$37.14	$37.15	$37.10
Purchase #2	$53.52	4.421%	$55.8861	$55.89	$55.90	$55.90
Purchase #3	$75.83	8.652%	$82.3908	$82.39	$82.40	$82.40
Purchase #4	$162.84	6.816%	$173.9392	$173.94	$173.95	$173.90
Purchase #5	$98.61	13.466%	$111.8888	$111.89	$111.90	$111.90
Purchase #6	$246.68	10.206%	$271.8562	$271.86	$271.85	$271.90
Purchase #7	$185.92	8.855%	$202.3832	$202.38	$202.40	$202.40
7 purchase totals =	$856.98		$935.4875	$935.49	$935.55	$935.50