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	$82.29	5.456%	$86.7797	$86.78	$86.80	$86.80
Purchase #2	$100.65	3.183%	$103.8537	$103.85	$103.85	$103.90
Purchase #3	$151.70	6.257%	$161.1919	$161.19	$161.20	$161.20
Purchase #4	$226.85	5.319%	$238.9162	$238.92	$238.90	$238.90
Purchase #5	$76.87	12.343%	$86.3581	$86.36	$86.35	$86.40
Purchase #6	$152.78	3.447%	$158.0463	$158.05	$158.05	$158.00
Purchase #7	$228.79	11.533%	$255.1764	$255.18	$255.20	$255.20
7 purchase totals =	$1,019.93		$1,090.3223	$1,090.33	$1,090.35	$1,090.40