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	$205.95	10.437%	$227.445	$227.45	$227.45	$227.40
Purchase #2	$85.74	4.321%	$89.4448	$89.44	$89.45	$89.40
Purchase #3	$156.66	4.197%	$163.235	$163.24	$163.25	$163.20
Purchase #4	$54.90	13.358%	$62.2335	$62.23	$62.25	$62.20
Purchase #5	$99.32	11.787%	$111.0268	$111.03	$111.05	$111.00
Purchase #6	$141.28	3.219%	$145.8278	$145.83	$145.85	$145.80
Purchase #7	$108.75	6.419%	$115.7307	$115.73	$115.75	$115.70
7 purchase totals =	$852.60		$914.9436	$914.95	$915.05	$914.70