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	$226.53	10.563%	$250.4584	$250.46	$250.45	$250.50
Purchase #2	$175.95	6.429%	$187.2618	$187.26	$187.25	$187.30
Purchase #3	$149.70	13.254%	$169.5412	$169.54	$169.55	$169.50
Purchase #4	$105.25	13.603%	$119.5672	$119.57	$119.55	$119.60
Purchase #5	$130.94	4.555%	$136.9043	$136.90	$136.90	$136.90
Purchase #6	$146.82	3.493%	$151.9484	$151.95	$151.95	$151.90
Purchase #7	$145.33	13.290%	$164.6444	$164.64	$164.65	$164.60
7 purchase totals =	$1,080.52		$1,180.3257	$1,180.32	$1,180.30	$1,180.30