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	$111.53	8.512%	$121.0234	$121.02	$121.00	$121.00
Purchase #2	$90.85	6.800%	$97.0278	$97.03	$97.05	$97.00
Purchase #3	$40.82	3.143%	$42.103	$42.10	$42.10	$42.10
Purchase #4	$157.94	4.348%	$164.8072	$164.81	$164.80	$164.80
Purchase #5	$127.87	12.662%	$144.0609	$144.06	$144.05	$144.10
Purchase #6	$138.82	4.550%	$145.1363	$145.14	$145.15	$145.10
Purchase #7	$156.82	3.381%	$162.1221	$162.12	$162.10	$162.10
7 purchase totals =	$824.65		$876.2807	$876.28	$876.25	$876.20