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	$181.40	10.746%	$200.8932	$200.89	$200.90	$200.90
Purchase #2	$169.54	6.682%	$180.8687	$180.87	$180.85	$180.90
Purchase #3	$66.90	5.531%	$70.6002	$70.60	$70.60	$70.60
Purchase #4	$83.34	7.783%	$89.8264	$89.83	$89.85	$89.80
Purchase #5	$103.53	5.866%	$109.6031	$109.60	$109.60	$109.60
Purchase #6	$98.73	3.568%	$102.2527	$102.25	$102.25	$102.30
Purchase #7	$96.69	11.791%	$108.0907	$108.09	$108.10	$108.10
7 purchase totals =	$800.13		$862.1350	$862.13	$862.15	$862.20