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	$176.67	13.196%	$199.9834	$199.98	$200.00	$200.00
Purchase #2	$31.58	6.512%	$33.6365	$33.64	$33.65	$33.60
Purchase #3	$127.63	5.533%	$134.6918	$134.69	$134.70	$134.70
Purchase #4	$236.59	8.499%	$256.6978	$256.70	$256.70	$256.70
Purchase #5	$148.57	6.529%	$158.2701	$158.27	$158.25	$158.30
Purchase #6	$53.49	11.242%	$59.5033	$59.50	$59.50	$59.50
Purchase #7	$155.32	7.627%	$167.1663	$167.17	$167.15	$167.20
7 purchase totals =	$929.85		$1,009.9492	$1,009.95	$1,009.95	$1,010.00