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	$207.67	5.682%	$219.4698	$219.47	$219.45	$219.50
Purchase #2	$41.70	8.725%	$45.3383	$45.34	$45.35	$45.30
Purchase #3	$244.97	4.461%	$255.8981	$255.90	$255.90	$255.90
Purchase #4	$69.85	12.661%	$78.6937	$78.69	$78.70	$78.70
Purchase #5	$201.40	10.864%	$223.2801	$223.28	$223.30	$223.30
Purchase #6	$179.66	5.835%	$190.1432	$190.14	$190.15	$190.10
Purchase #7	$232.52	13.517%	$263.9497	$263.95	$263.95	$263.90
7 purchase totals =	$1,177.77		$1,276.7729	$1,276.77	$1,276.80	$1,276.70