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	$183.29	12.275%	$205.7888	$205.79	$205.80	$205.80
Purchase #2	$112.91	6.229%	$119.9432	$119.94	$119.95	$119.90
Purchase #3	$231.37	6.699%	$246.8695	$246.87	$246.85	$246.90
Purchase #4	$84.65	6.728%	$90.3453	$90.35	$90.35	$90.30
Purchase #5	$241.46	7.140%	$258.7002	$258.70	$258.70	$258.70
Purchase #6	$85.41	7.761%	$92.0387	$92.04	$92.05	$92.00
Purchase #7	$126.28	4.166%	$131.5408	$131.54	$131.55	$131.50
7 purchase totals =	$1,065.37		$1,145.2265	$1,145.23	$1,145.25	$1,145.10