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	$200.30	6.780%	$213.8803	$213.88	$213.90	$213.90
Purchase #2	$41.37	4.725%	$43.3247	$43.32	$43.30	$43.30
Purchase #3	$48.80	9.769%	$53.5673	$53.57	$53.55	$53.60
Purchase #4	$102.53	6.496%	$109.1903	$109.19	$109.20	$109.20
Purchase #5	$93.55	11.248%	$104.0725	$104.07	$104.05	$104.10
Purchase #6	$55.40	10.712%	$61.3344	$61.33	$61.35	$61.30
Purchase #7	$137.93	3.368%	$142.5755	$142.58	$142.60	$142.60
7 purchase totals =	$679.88		$727.9450	$727.94	$727.95	$728.00