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	$208.90	12.514%	$235.0417	$235.04	$235.05	$235.00
Purchase #2	$210.80	9.864%	$231.5933	$231.59	$231.60	$231.60
Purchase #3	$59.57	4.621%	$62.3227	$62.32	$62.30	$62.30
Purchase #4	$166.70	5.628%	$176.0819	$176.08	$176.10	$176.10
Purchase #5	$113.43	12.751%	$127.8935	$127.89	$127.90	$127.90
Purchase #6	$93.34	12.398%	$104.9123	$104.91	$104.90	$104.90
Purchase #7	$89.65	9.669%	$98.3183	$98.32	$98.30	$98.30
7 purchase totals =	$942.39		$1,036.1637	$1,036.15	$1,036.15	$1,036.10