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	$227.31	13.501%	$257.9991	$258.00	$258.00	$258.00
Purchase #2	$20.98	8.680%	$22.8011	$22.80	$22.80	$22.80
Purchase #3	$231.48	4.328%	$241.4985	$241.50	$241.50	$241.50
Purchase #4	$175.95	11.760%	$196.6417	$196.64	$196.65	$196.60
Purchase #5	$239.25	12.153%	$268.3261	$268.33	$268.35	$268.30
Purchase #6	$238.56	11.715%	$266.5073	$266.51	$266.50	$266.50
Purchase #7	$158.49	9.122%	$172.9475	$172.95	$172.95	$172.90
7 purchase totals =	$1,292.02		$1,426.7213	$1,426.73	$1,426.75	$1,426.60