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	$243.94	10.779%	$270.2343	$270.23	$270.25	$270.20
Purchase #2	$48.32	8.855%	$52.5987	$52.60	$52.60	$52.60
Purchase #3	$246.39	8.155%	$266.4831	$266.48	$266.50	$266.50
Purchase #4	$144.30	7.322%	$154.8656	$154.87	$154.85	$154.90
Purchase #5	$102.93	13.227%	$116.5446	$116.54	$116.55	$116.50
Purchase #6	$135.30	7.586%	$145.5639	$145.56	$145.55	$145.60
Purchase #7	$138.68	5.218%	$145.9163	$145.92	$145.90	$145.90
7 purchase totals =	$1,059.86		$1,152.2065	$1,152.20	$1,152.20	$1,152.20