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	$137.39	4.683%	$143.824	$143.82	$143.80	$143.80
Purchase #2	$93.42	7.407%	$100.3396	$100.34	$100.35	$100.30
Purchase #3	$84.70	4.503%	$88.514	$88.51	$88.50	$88.50
Purchase #4	$107.98	7.613%	$116.2005	$116.20	$116.20	$116.20
Purchase #5	$190.43	8.332%	$206.2966	$206.30	$206.30	$206.30
Purchase #6	$145.33	4.166%	$151.3844	$151.38	$151.40	$151.40
Purchase #7	$37.90	6.335%	$40.301	$40.30	$40.30	$40.30
7 purchase totals =	$797.15		$846.8601	$846.85	$846.85	$846.80