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	$114.27	10.678%	$126.4718	$126.47	$126.45	$126.50
Purchase #2	$39.69	3.151%	$40.9406	$40.94	$40.95	$40.90
Purchase #3	$164.58	10.227%	$181.4116	$181.41	$181.40	$181.40
Purchase #4	$118.45	13.109%	$133.9776	$133.98	$134.00	$134.00
Purchase #5	$238.94	10.112%	$263.1016	$263.10	$263.10	$263.10
Purchase #6	$248.45	7.492%	$267.0639	$267.06	$267.05	$267.10
Purchase #7	$94.94	3.215%	$97.9923	$97.99	$98.00	$98.00
7 purchase totals =	$1,019.32		$1,110.9594	$1,110.95	$1,110.95	$1,111.00