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	$228.91	11.732%	$255.7657	$255.77	$255.75	$255.80
Purchase #2	$64.27	10.441%	$70.9804	$70.98	$71.00	$71.00
Purchase #3	$141.56	11.672%	$158.0829	$158.08	$158.10	$158.10
Purchase #4	$216.59	5.388%	$228.2599	$228.26	$228.25	$228.30
Purchase #5	$22.64	3.737%	$23.4861	$23.49	$23.50	$23.50
Purchase #6	$93.52	6.804%	$99.8831	$99.88	$99.90	$99.90
Purchase #7	$220.40	8.186%	$238.4419	$238.44	$238.45	$238.40
7 purchase totals =	$987.89		$1,074.9000	$1,074.90	$1,074.95	$1,075.00