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	$226.26	7.555%	$243.3539	$243.35	$243.35	$243.40
Purchase #2	$73.54	12.704%	$82.8825	$82.88	$82.90	$82.90
Purchase #3	$123.49	6.588%	$131.6255	$131.63	$131.65	$131.60
Purchase #4	$13.40	10.623%	$14.8235	$14.82	$14.80	$14.80
Purchase #5	$114.90	13.617%	$130.5459	$130.55	$130.55	$130.50
Purchase #6	$116.34	8.169%	$125.8438	$125.84	$125.85	$125.80
Purchase #7	$120.50	5.702%	$127.3709	$127.37	$127.35	$127.40
7 purchase totals =	$788.43		$856.4460	$856.44	$856.45	$856.40