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	$173.34	5.613%	$183.0696	$183.07	$183.05	$183.10
Purchase #2	$117.31	9.831%	$128.8427	$128.84	$128.85	$128.80
Purchase #3	$73.38	12.556%	$82.5936	$82.59	$82.60	$82.60
Purchase #4	$107.94	3.446%	$111.6596	$111.66	$111.65	$111.70
Purchase #5	$121.28	4.478%	$126.7109	$126.71	$126.70	$126.70
Purchase #6	$191.90	7.870%	$207.0025	$207.00	$207.00	$207.00
Purchase #7	$211.31	9.443%	$231.264	$231.26	$231.25	$231.30
7 purchase totals =	$996.46		$1,071.1429	$1,071.13	$1,071.10	$1,071.20