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	$144.77	9.247%	$158.1569	$158.16	$158.15	$158.20
Purchase #2	$211.72	6.686%	$225.8756	$225.88	$225.90	$225.90
Purchase #3	$178.66	13.805%	$203.324	$203.32	$203.30	$203.30
Purchase #4	$184.47	4.194%	$192.2067	$192.21	$192.20	$192.20
Purchase #5	$105.85	13.476%	$120.1143	$120.11	$120.10	$120.10
Purchase #6	$152.43	10.853%	$168.9732	$168.97	$168.95	$169.00
Purchase #7	$78.49	13.853%	$89.3632	$89.36	$89.35	$89.40
7 purchase totals =	$1,056.39		$1,158.0139	$1,158.01	$1,157.95	$1,158.10