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	$234.37	9.559%	$256.7734	$256.77	$256.75	$256.80
Purchase #2	$52.39	6.698%	$55.8991	$55.90	$55.90	$55.90
Purchase #3	$182.79	8.414%	$198.17	$198.17	$198.15	$198.20
Purchase #4	$203.84	9.160%	$222.5117	$222.51	$222.50	$222.50
Purchase #5	$211.43	10.193%	$232.9811	$232.98	$233.00	$233.00
Purchase #6	$17.64	5.265%	$18.5687	$18.57	$18.55	$18.60
Purchase #7	$81.82	10.515%	$90.4234	$90.42	$90.40	$90.40
7 purchase totals =	$984.28		$1,075.3274	$1,075.32	$1,075.25	$1,075.40