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	$81.95	12.814%	$92.4511	$92.45	$92.45	$92.50
Purchase #2	$212.93	8.687%	$231.4272	$231.43	$231.45	$231.40
Purchase #3	$36.85	13.517%	$41.831	$41.83	$41.85	$41.80
Purchase #4	$183.32	6.148%	$194.5905	$194.59	$194.60	$194.60
Purchase #5	$105.79	11.429%	$117.8807	$117.88	$117.90	$117.90
Purchase #6	$173.50	11.798%	$193.9695	$193.97	$193.95	$194.00
Purchase #7	$140.72	3.681%	$145.8999	$145.90	$145.90	$145.90
7 purchase totals =	$935.06		$1,018.0499	$1,018.05	$1,018.10	$1,018.10