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	$167.84	13.849%	$191.0842	$191.08	$191.10	$191.10
Purchase #2	$61.27	12.393%	$68.8632	$68.86	$68.85	$68.90
Purchase #3	$204.96	5.656%	$216.5525	$216.55	$216.55	$216.60
Purchase #4	$204.64	5.745%	$216.3966	$216.40	$216.40	$216.40
Purchase #5	$228.72	6.233%	$242.9761	$242.98	$243.00	$243.00
Purchase #6	$208.52	10.337%	$230.0747	$230.07	$230.05	$230.10
Purchase #7	$83.93	6.425%	$89.3225	$89.32	$89.30	$89.30
7 purchase totals =	$1,159.88		$1,255.2698	$1,255.26	$1,255.25	$1,255.40