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	$102.76	13.800%	$116.9409	$116.94	$116.95	$116.90
Purchase #2	$233.65	12.199%	$262.153	$262.15	$262.15	$262.20
Purchase #3	$139.84	4.712%	$146.4293	$146.43	$146.45	$146.40
Purchase #4	$174.32	8.141%	$188.5114	$188.51	$188.50	$188.50
Purchase #5	$12.46	6.486%	$13.2682	$13.27	$13.25	$13.30
Purchase #6	$188.66	9.490%	$206.5638	$206.56	$206.55	$206.60
Purchase #7	$66.63	10.606%	$73.6968	$73.70	$73.70	$73.70
7 purchase totals =	$918.32		$1,007.5634	$1,007.56	$1,007.55	$1,007.60