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	$215.36	10.402%	$237.7617	$237.76	$237.75	$237.80
Purchase #2	$114.74	7.710%	$123.5865	$123.59	$123.60	$123.60
Purchase #3	$235.45	8.587%	$255.6681	$255.67	$255.65	$255.70
Purchase #4	$185.54	10.123%	$204.3222	$204.32	$204.30	$204.30
Purchase #5	$144.75	3.110%	$149.2517	$149.25	$149.25	$149.30
Purchase #6	$61.81	8.106%	$66.8203	$66.82	$66.80	$66.80
Purchase #7	$174.48	6.224%	$185.3396	$185.34	$185.35	$185.30
7 purchase totals =	$1,132.13		$1,222.7501	$1,222.75	$1,222.70	$1,222.80