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	$65.51	10.341%	$72.2844	$72.28	$72.30	$72.30
Purchase #2	$123.74	7.563%	$133.0985	$133.10	$133.10	$133.10
Purchase #3	$7.37	6.463%	$7.8463	$7.85	$7.85	$7.80
Purchase #4	$150.30	10.815%	$166.5549	$166.55	$166.55	$166.60
Purchase #5	$221.56	12.616%	$249.512	$249.51	$249.50	$249.50
Purchase #6	$223.87	6.837%	$239.176	$239.18	$239.20	$239.20
Purchase #7	$155.29	10.854%	$172.1452	$172.15	$172.15	$172.10
7 purchase totals =	$947.64		$1,040.6173	$1,040.62	$1,040.65	$1,040.60